Sighere was the joint king of the Kingdom of Essex

Essex

Essex is a ceremonial and non-metropolitan county in the East region of England, and one of the home counties. It is located to the northeast of Greater London. It borders with Cambridgeshire and Suffolk to the north, Hertfordshire to the west, Kent to the South and London to the south west...

 along with his brother Sebbi

Sebbi of Essex

Sebbi was the joint King of Essex from 664 to 683 along with his brother, Sighere. After Sighere died, Sebbi became sole ruler of Essex until 694....

 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

Swithelm of Essex

Swithelm was King of Essex from 660 to 664.Swithelm succeeded King Sigeberht II after he, along with his brother Swithfrith, murdered him. They accused him of being too friendly toward Christians. In 662, however, he was persuaded to convert to Christianity by Aethelwald, king of East Anglia. ...

. While Sighere returned to paganism

Anglo-Saxon polytheism

Anglo-Saxon paganism, or as it has also been known, Anglo-Saxon heathenism,The religion has been referred to as "paganism" by most scholars, such as David M. Wilson and Martin Carver , but as "heathenism" by some others, like Brian Branston...

, Sebbi remained Christian

Christian

A Christian is a person who adheres to Christianity, an Abrahamic, monotheistic religion based on the life and teachings of Jesus of Nazareth as recorded in the Canonical gospels and the letters of the New Testament...

. They soon developed a rivalry. Sighere found an ally in Wessex

Wessex

The Kingdom of Wessex or Kingdom of the West Saxons was an Anglo-Saxon kingdom of the West Saxons, in South West England, from the 6th century, until the emergence of a united English state in the 10th century, under the Wessex dynasty. It was to be an earldom after Canute the Great's conquest...

, and Sebbi in Mercia

Mercia

Mercia was one of the kingdoms of the Anglo-Saxon Heptarchy. It was centred on the valley of the River Trent and its tributaries in the region now known as the English Midlands...

. As a result of their rivalry, King Wulfhere of Mercia

Wulfhere of Mercia

Wulfhere was King of Mercia from the end of the 650s until 675. He was the first Christian king of all of Mercia, though it is not known when or how he converted from Anglo-Saxon paganism. His accession marked the end of Oswiu of Northumbria's overlordship of southern England, and Wulfhere...

 established himself as overlord of Essex. and induced Sighere to marry his niece Osyth, daughter of Firthuwold, sub-king of Surrey. Jaruman

Jaruman

Jaruman was the fourth Bishop of Mercia. He fought against apostasy outside his diocese. He served as bishop in the time of King Wulfhere of Mercia, on whose behalf he undertook several missions to Saxon tribes which had lapsed into paganism...

, 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

North Elmham

North Elmham is a village and civil parish in the English county of Norfolk.It covers an area of and had a population of 1,428 in 624 households as of the 2001 census. For the purposes of local government, it falls within the district of Breckland....

. Sighere died in 683, and Sebbi became sole ruler of Essex.