He is married to actress Guðlaug María Bjarnadóttir and they have three children. He studied interior design in Copenhagen and literature and theater in Copenhagen and Strasbourg from 1965-1972.
Símonarson mainly writes for the stage and is one of the most respected and popular dramatists in Iceland. He is a very versatile writer having also written numerous novels, colletions of short stories and poetry and children's books. His songs and lyrics for children have been released on records and CDs.
Símonarson has mainly worked as full-time writer since 1974. He was director of the People's Theatre in Reykjavík 1980-1982, Chairman of the Icelandic Dramatists´ Union 1986-1999, Vice-Chairman of I.T.I.s´ (International Theatre Institut) playwrights´ committee 1993-1998. Honorary Member of the I.T.I.s´ Playwrights´ Forum. Símonarson has been on the board of the Icelandic Writers Union and the Society of Composers and Copyright Owners since 1985. He is an honorary member of The Icelandic Playwrights Union.