A sibling is one of two or more individuals having one or both parents in common. A female sibling is a sister and a male sibling is a brother. In most societies throughout the world, siblings usually grow up together, facilitating the development of strong emotional bonds such as love, or thoughtfulness. The emotional bond between siblings is often complicated and is influenced by factors such as parental treatment, birth order, personality, and personal experiences outside the family.
Identical twins share 100% of their DNA. Full siblings are first-degree relatives and, on average, share 50% of their genes out of those that vary among humans. Half-siblings are second-degree relatives and have, on average, have a 25% overlap in their human genetic variation.
- 1 Types of siblings
- 2 Birth order
- 3 Regressive behavior at the birth of a new sibling
- 4 Sibling rivalry
- 5 Westermarck effect and its opposite
- 6 Famous sibling groups
- 7 See also
- 8 Notes
- 9 External links
Types of siblings
Full siblings (full brothers or full sisters) share the same biological parents and are 50% related (full siblings share 50% of their genes out of those that vary among humans). Identical twins by definition are 100% related.
Half-siblings only share one parent instead of two as full siblings do and on average 25% related, i.e. the children that the parent and stepparent (i.e. mother and stepfather, or father and stepmother) have together. Theoretically, there is a chance that they might not be related at all though this is very rare and is due to there being a smaller possibility of inheriting the same chromosomes from the shared parent. Half-siblings can have a wide variety of interpersonal relationships, from a bond as close as any full siblings, to total strangers. Some consider their paternal siblings their "sibling on their father's side" and some consider their maternal sibling just their "sibling" because they give more weight to a shared mother and womb, and because children are usually raised by and/or have more interaction with their mother.
There are specific terms for referring to half-siblings based on the sex of the shared parent:
- Those that share the same mother (but different fathers) are known as uterine siblings or maternal half-brothers/half-sisters.
- Those that share the same father (but different mothers) are known as agnate siblings or paternal half-brothers/half-sisters. In law, the term consanguine is used in place of agnate.
In law (and especially inheritance law), half-siblings were often accorded unequal treatment. Old English common law at one time incorporated inequalities into the laws of intestate succession, with half-siblings taking only half as much property of their intestate siblings' estates as other siblings of full-blood. Unequal treatment of this type has been wholly abolished in England and throughout the United States.
Three-quarter siblings have one common parent, while their unshared parents have a mean consanguanuity of 50%. This includes full siblings and parent/child. (Similar terminology is used in horse breeding, where it occurs more frequently). Three-quarter siblings share more genes than half siblings, but fewer than full siblings. There are two genetic scenarios for 3/4 siblings:
In this case the unshared parents are full siblings. Furthermore, the three-quarter siblings are also first cousins. An example of this is that of Charles Lindbergh's children with his mistress Brigitte Hesshaimer, and his children with her sister, Marietta Hesshaimer. Another recent example relates to Jermaine and Randy Jackson, of the Jackson 5, who have both fathered children with Alejandra Genevieve Oaziaza.
In the case where the unshared parents are identical twins, the children share as much genetic material as full siblings do.
In this case a woman has children with two men who are father and son, or a man has children with two women who are mother and daughter. These children will be three-quarter siblings.
"Stepsiblings" (stepbrothers or stepsisters) are the children of one's stepparent from a previous relationship. They are not, however, related by blood.
"Milk siblings" are children breastfed by either a woman who is the mother of one of the two babies, or by someone other than their biological mother, the latter a practice known as wetnursing and once widespread in the developed world, as it still is in parts of the developing world.
In Islam those who are fed in this way become siblings to the biological children of their wetnurse, provided that they are less than 2 years old. Islamic law (shariah) codifies the relationship between these people, and certain specified relatives, as rada'a; given that a child is breastfed five fulfilling (satisfactory to him) times, once they are adult, they are mahram, meaning that they are not allowed to marry each other, and the rules of modesty known as purdah are relaxed, as with other family members. But, laws of inheritance do not apply in the case of milk siblings.
"Foster siblings" are children who are raised in the same foster home, foster children of the person's parents, or foster parents' biological children.
"Adoptive siblings" are when two children are legally related, but are not related by blood. Adopted siblings are not biologically related but may consider each other siblings because they act like they are.
- Adoptive siblings that are adopted by both legal parents are considered full adoptive siblings.
- Adoptive siblings that are adopted by only the same legal mother are maternal adoptive half siblings.
- Adoptive siblings that are adopted by only the same legal father are paternal adoptive half siblings.
"Cross siblings" are two unrelated people who share one or more half-siblings (not to be confused with stepsiblings, as described earlier). For example, in The Young and the Restless, Michael is the maternal half sibling of Kevin, and the paternal half sibling of Eden. In this case, Kevin and Eden are cross siblings - they share no blood. In Desperate Housewives, M.J. Delfino and Julie Mayer share a mother, and Julie and Evan Mayer share a father, so M.J. and Evan are cross siblings.
"Sibling cousins" are those who have the same mother with their fathers being brothers or cousins, or who share the same father with their mothers being sisters or cousins. This is a broader category than, but inclusive of, the horizontal 3/4 sibling above.
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Birth order is a person's rank by age among his or her siblings. Typically, researchers classify siblings as "eldest", "middle child", and "youngest" or simply distinguish between "firstborn" and "later born" children.
Birth order is commonly believed in pop psychology and popular culture to have a profound and lasting effect on psychological development and personality. For example, firstborns are seen as conservative and high achieving, middle children as natural mediators, and youngest children as charming and outgoing. In his book Born to Rebel, Frank Sulloway argues that firstborns are more conscientious, more socially dominant, less agreeable, and less open to new ideas compared to laterborns. Literature reviews that have examined many studies and attempted to control for confounding variables tend to find minimal effects for birth order on personality. In her review of the scientific literature, Judith Rich Harris suggests that birth order effects may exist within the context of the family of origin, but that they are not enduring aspects of personality.
In practice, systematic birth order research is a challenge because it is difficult to control for all of the variables that are statistically related to birth order. For example, large families are generally lower in socioeconomic status than small families, so third born children are more likely than firstborn children to come from poorer families. Spacing of children, parenting style, and gender are additional variables to consider.
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Regressive behavior at the birth of a new sibling
The arrival of a new baby is especially stressful for firstborns and for siblings between 3 and 5 years old. Regressive behavior and aggressive behavior, such as handling the baby roughly, can also occur. All of these symptoms are considered to be typical and developmentally appropriate for children between the ages of 3–5. While some can be prevented, the remainder can be improved within a few months. Regressive behavior may include demand for a bottle, thumb sucking, requests to wear diapers (even if toilet-trained), or requests to carry a security blanket.
Regressive behaviors are the child's way of demanding the parents' love and attention.
The American Academy of Pediatrics suggests that instead of protesting or telling children to act their age, parents should simply grant their requests without becoming upset. The affected children will soon return to their normal routine when they realize that they now have just as important a place in the family as the new sibling. Most of the behaviors can be improved within a few months.
The University of Michigan Health System advises that most occurrences of regressive behavior are mild and to be expected; however, it recommends parents to contact a pediatrician or child psychologist if the older child tries to hurt the baby, if regressive behavior does not improve within 2 or 3 months, or if the parents have other questions or concerns.
"Sibling rivalry" is a type of competition or animosity among brothers and sisters. It appears to be particularly intense when children are very close in age or of the same gender. Sibling rivalry can involve aggression; however, it is not the same as sibling abuse where one child victimizes another.
Sibling rivalry usually starts right after, or before, the arrival of the second child. While siblings will still love each other, it is not uncommon for them to bicker and be malicious to each other. Children are sensitive from the age of 1 year to differences in parental treatment and by 3 years they have a sophisticated grasp of family rules and can evaluate themselves in relation to their siblings. Sibling rivalry often continues throughout childhood and can be very frustrating and stressful to parents. One study found that the age group 10–15 reported the highest level of competition between siblings. Sibling rivalry can continue into adulthood and sibling relationships can change dramatically over the years. Approximately one-third of adults describe their relationship with siblings as rivalrous or distant. However, rivalry often lessens over time and at least 80% of siblings over age 60 enjoy close ties.
Each child in a family competes to define who they are as persons and want to show that they are separate from their siblings. Sibling rivalry increases when children feel they are getting unequal amounts of their parents' attention, where there is stress in the parents' and children's lives, and where fighting is accepted by the family as a way to resolve conflicts. Sigmund Freud saw the sibling relationship as an extension of the Oedipus complex, where brothers were in competition for their mother's attention and sisters for their father's. Evolutionary psychologists explain sibling rivalry in terms of parental investment and kin selection: a parent is inclined to spread resources equally among all children in the family, but a child wants most of the resources for him or herself.
Westermarck effect and its opposite
Anthropologist Edvard Westermarck found that children who are brought up together as siblings are desensitized to form sexual attraction to one another later in life. This is known as the Westermarck Effect. It can be seen in biological and adoptive families, but also in other situations where children are brought up in close contact, such as the Israeli kibbutz system and the Chinese Shim-pua marriage.
The opposite phenomenon, when relatives do fall in love, is known as genetic sexual attraction. This can occur between siblings brought up apart from each other, for example, adoptees who are re-united in adulthood.
Famous sibling groups
- The Koch brothers
- Naturalist Alexander Humboldt and philosopher Wilhelm von Humboldt
- The Marx Brothers comedians actors
- The Grimm Brothers, folklorists and anthropologists
- Otto and Gregor Strasser, leaders of a dissident brand of Naziism
- Intellectuals Julian, Aldous and their step brother Andrew Huxley of the Huxley family
- The Kardashians, reality television stars and American socialites: Kourtney, Kim, Khloé and Rob
- The children of Olympian Bruce Jenner, reality television stars and half siblings of the Kardashians: Kendall, Kylie, Burt, Casey (b. June 10, 1980), Brandon (b. June 4, 1981) and Brody Jenner (b. August 21, 1983, half sibling of Kendall and Kylie).
- The Wayans Brothers, directors, screenwriters and actors
- The Olsen twins: Mary-Kate and Ashley
- The Smothers Brothers, comedians: Tom and Dick
- The Wright Brothers, aviation pioneers and inventors: Orville and Wilbur
- The Dionne quintuplets
- Isabelle and Paul Duchesnay, world champion figure skaters.
- Sprouse brothers, American actors: Dylan and Cole
- Sutter brothers, Canadian family who played or have been associated with the National Hockey League.
- Steve and Mark Waugh, Australian cricketers.
- Marc and Pau Gasol, basketball players
- Duncan II, Edgar, Alexander I and David I, kings of Scotland
- The Black Douglases, clashed with King James II of Scotland: William, James, Archibald, Hugh and John
- The actresses Olivia de Havilland and Joan Fontaine
- The Chapman brothers, Duane Lee Chapman, II and Leland Chapman, stars of Dog The Bounty Hunter
- Thirty Seconds to Mars, an American rock band, Jared and Shannon Leto
- A, an English rock band, Jason Perry & Adam Perry (identical twins) & Giles Perry
- Nelson, An American Rock Band, Matthew Nelson & Gunnar Nelson (Identical Twins)
- AC/DC, an Australian rock band, Malcolm and Angus Young
- Ace of Base, a Swedish quartet consisting of the three Berggren siblings and family friend Ulf Ekberg
- The Allman Brothers Band, an American southern jam band led by Gregg Allman and the late Duane Allman.
- Anathema, an English band, formerly death-doom metal, later alternative rock, Daniel, Vincent and Jamie Cavanagh; John and Lee Douglas
- The Andrews Sisters, an American close harmony singing group, LaVerne Sophia, Maxene Angelyn and Patricia "Patty" Marie Andrews
- Architects, British rock band, Dan and Tom Searle (Twins)
- Arch Enemy, a Swedish melodic death metal band, Michael and Christopher Amott
- Beach Boys, an American rock band, Brian, Carl and Dennis Wilson
- BeBe & CeCe Winans, American gospel music brother and sister duo
- The Bee Gees, a British harmonic "soft rock" act, Barry, Robin and Maurice Gibb
- Biffy Clyro, A Scottish Rock Band, James Johnston & Ben Johnston (identical twins)
- Blue October, Justin and Jeremy Furstenfeld
- Boards of Canada, are a Scottish electronic music duo consisting of brothers Mike Sandison and Marcus Eoin.
- The Boswell Sisters, an American close harmony singing group, Martha Connee and Helvetia "Vet" Boswell
- Boyfriend, South Korean boy band with identical twins, Jo Youngmin and Jo Kwangmin (commonly known as the 'Jo Twins')
- The Burns Sisters, folk/pop/rock trio with a Celtic slant
- The Carpenters, American melodic pop duo, Karen and Richard Carpenter.
- Cavalera Conspiracy, a Brazilian heavy metal supergroup, Max and Igor Cavalera
- Cheeky Girls, a Romanian pop music duo, Gabriela and Monica Irimia
- Chevelle, an American rock trio, Pete, Sam and Joe Loeffler
- Collective Soul, an American Post-Grunge band, Ed Roland and Dean Roland
- The Corrs, a Celtic folk rock band, Andrea, Sharon, Caroline and Jim Corr
- The Cowsills, an American popular music family band. Bill, Bob, Paul, Barry, John, Susan and Mom, Barbara.
- Creedence Clearwater Revival, an American rock band, John Fogerty and Tom Fogerty
- The Cribs, indie rock band, Gary Jarman, Ryan Jarman (identical twins) & Ross Jarman
- The Darkness, an English rock band, Justin Hawkins and Dan Hawkins.
- DEVO, an American new-wave band, Mark and Bob Mothersbaugh, and Gerald and Bob Casale
- Dixie Chicks, an American country music group Martie Maguire and Emily Robison
- The Everly Brothers, an American country-influenced band, Philip and Isaac Donald Everly.
- Good Charlotte, an American pop punk band, Joel and Benji Madden (identical twins)
- Halestorm, an American hard rock band, Arejay and Lzzy Hale
- Hanson, an American pop rock band, Isaac, Taylor, and Zac Hanson
- Heart, an American rock band, Ann and Nancy Wilson
- The Hives, Swedish Rock Band, Pelle Almqvist and Niklas Almqvist
- INXS had three Farriss brothers
- Jackson 5, an American popular music family group, Jackie, Tito, Jermaine, Marlon and Michael Jackson (And also Randy when Jermaine left.)
- Jonas Brothers, an American Disney pop rock band, Kevin, Joe, and Nick Jonas
- Kalmah, a Finnish melodic death metal band, Pekka and Antti Kokko.
- Kings of Leon, an American rock band, Caleb, Nathan and Jared Followill
- The Kinks, an English rock band, Ray and Dave Davies
- Lamb of God, an American metal band, Will and Chris Adler
- The Maccabees, British indie rock band, brothers Felix, Hugo and Will White
- Madina Lake, an American rock band, Nathan Leone & Matthew Leone (identical twins)
- The Magic Numbers, an English rock band, Angela Gannon & Sean Gannon/Michele Stodart & Romeo Stodart
- Misery Signals, an American hardcore band, Brandon and Ryan Morgan
- The Moffatts, a Canadian pop/rock band, Scott and triplets Bob, Clint, and Dave. The fraternal twins Bob and Clint later formed a duo called Same Same.
- My Chemical Romance, an American rock band, Mikey and Gerard Way
- Naked Brothers Band an American rock band Alex Wolff and Nat Wolff
- The National, an American rock band, Bryce and Aaron Dessner, Scott and Bryan Devendorf
- Nazia and Zoheb, were a Pakistani Pop group, Nazia Hassan, Zoheb Hassan
- Nickleback, a Canadian rock band, Chad, Mike and Brandon Kroeger
- No Doubt, an American rock band, Gwen and Eric Stefani
- The Nolans, an Irish/English family music group, Bernie Nolan, Anne Nolan, Maureen Nolan, Linda Nolan, Coleen Nolan, Denise Nolan
- October Tide, a Swedish metal band, Fredrik and Mattais Norrman
- Oasis, an English rock band, Liam and Noel Gallagher
- Olsen Brothers, Danish pop-rock duo
- The Osmonds, an American family music group, Alan, Wanyne, Merrill, Jay, Donny, Marie and Jimmy Osmond
- Pantera, an American heavy metal band, Dimebag Darrell and Vinnie Paul
- Paramore, an American rock band, Josh and Zac Farro
- Pierce the Veil, an American experimental post-hardcore band, Vic and Mike Fuentes
- The Proclaimers, A Scottish Vocal Band, Charlie Reid & Craig Reid
- Radiohead, an English alternative rock band, Jonny and Colin Greenwood
- Sister Sledge, an American musical group, Kim Sledge, Debbie Sledge, Joni Sledge, and Kathy Sledge
- Stone Temple Pilots, an American grunge/alternative rock band, Robert and Dean DeLeo
- Tegan and Sara, Canadian indie band, Tegan Rain and Sara Kiersten Quin (identical twins)
- Tokio Hotel, a German pop rock band, Bill and Tom Kaulitz
- UB40, an English reggae band, Ali Campbell and Robin Campbell
- Van Halen, an American heavy metal/hard rock band, Eddie, and Alex Van Halen
- The Veronicas, an Australian electropop pop-rock duo, Jessica and Lisa Origliasso
- Rufus and Martha Wainwright
- Wilson Phillips, an American pop group composed of sisters Wendy and Carnie Wilson, with Chynna Phillips
- Winters Brothers, rock musicians Johnny and Edgar
- YU grupa a Serbian rock band Dragi Jelic, Zika Jelic and Petar Jelic
- Young Guns, British rock band, brothers John and Fraser Taylor
- Tasty (band), twin brothers So-ryong and Dae-ryong
- Mersky Leder, Jane (Jan–Feb 1993). "Adult Sibling Rivalry". Psychology Today. Retrieved November 28, 2006.
- Dr. Shafer, Aaron. "Understanding genetics". The Tech. Stanford University. Retrieved 13 December 2013.
- Jermaine Jackson#Personal life
- Ernst, C. & Angst, J. (1983). Birth order: Its influence on personality. Springer.
- Jefferson, T., Herbst, J.H., & McCrae, R.R. (1998). Associations between birth order and personality traits: Evidence from self-reports and observer ratings. Journal of Research in Personality, 32, 498–509.
- Harris, J.R. (1998). The Nurture Assumption: Why children turn out the way they do. New York: Free Press.
- Carey, Benedict (June 21, 2007). "Family dynamics, not biology, behind higher IQ". International Herald Tribune. Retrieved July 15, 2007.
- Rodgers, J.L., Cleveland, H.H., van den Oord, E. and Rowe, D. (2000). Resolving the Debate Over Birth Order, Family Size and Intelligence. American Psychologist, Vol. 55.
- The Effects of Sibling Competition Syliva B. Rimm, Educational Assessment Service, 2002.
- New Baby Sibling University of Michigan Health System, June 2006
- Sibling Rivalry University of Michigan Health System, October 2006
- Sibling Rivalry in Degree and Dimensions Across the Lifespan Annie McNerney and Joy Usner, 30 April 2001.
- Freud Lecture: Juliet Mitchell, 2003
- Westermarck, E.A. (1921). The history of human marriage, 5th edn. London: Macmillan, 1921.
- Arthur P. Wolf. "Childhood Association and Sexual Attraction: A Further Test of the Westermarck Hypothesis". American Anthropologist, New Series, Vol. 72, No. 3 (Jun. 1970). pp. 503–515. Retrieved November 29, 2006.
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- Chisholm, Hugh, ed. (1911). "sister". Encyclopædia Britannica (11th ed.). Cambridge University Press.