Wulfhere was a younger son of King Penda. His older brother Peada accepted Christianity to marry the daughter of King Oswiu of Northumbria. After their father was killed by Oswiu, Peada was set up as a king of southern Mercia. Peada's wife murdered him within five months. Oswiu then took control of all Mercia and ruled it three years. The Mercian ealdormen Immin, Eafa and Eadbert rose up in rebellion against king Oswiu. Wulfhere, who had been kept hidden, was then proclaimed king. Wulfhere had little opposition from Oswiu as he was dealing with a rebellion in Northumbria. Wulfhere began building alliances with other kings in the south of England. His first may have been in about 660 when he married Ermenilda, the daughter of King Eorcenberht of Kent and his wife Seaxburh. About this same time he expanded Mercia to the west. He brought Shropshire and Herfordshire under his control. The kings of Essex submitted to his rule by 665.