Sighere was the joint king of the Kingdom of Essex along with his brother Sebbi from 664 to 683. He was outlived by Sebbi, who became the sole ruler of Essex after his death. Sighere and Sebbi were cousins of their predecessor Swithelm. While Sighere returned to paganism, Sebbi remained Christian. They soon developed a rivalry. Sighere found an ally in Wessex, and Sebbi with Mercia. As a result of their rivalry, King Wulfhere of Mercia established himself as overlord of Essex. and induced Sighere to marry his niece Osyth, daughter of Firthuwold, sub-king of Mercia in Surrey. Jaruman, the bishop of Mercia, was assigned to reconvert the people of Essex to Christianity. In 673, Sighere separated from Osyth, who then fled to the protection of Bishop Beaduwine of North Elmham. Sighere died in 683, and Sebbi became sole ruler of Essex.