Dynastic alliances bound Æthelwold's kingdom strongly to the Christian kingdom of Kent, where Seaxburh, the eldest daughter of Æthelwold's elder brother Anna, was Eorcenberht of Kent's queen. East Anglia's western stronghold in the Fens was held by Seaxburh's sister Æthelthryth and, like Kent, it was devoutly attached to the Roman Church. There was also an important Northumbrian connection: in 657, Hilda established the monastery of Streoneshalh (identified with Whitby), which later became the burial-place of Edwin and other Northumbrian kings. Hilda's sister Hereswitha married Æthelwold's youngest brother Æthelric in around 627–629.