Oswiu of Northumbria
When Oswiu and Eanflaed were married, he was raised in the Celtic church while she was raised in the Roman church. The main difference was how each calculated the date of Easter. Members of the Celtic church might be celebrating Easter while the Roman church was celebrating Lent. In 658 his son Alfrith, who now supported the Roman Church, replaced several of his Celtic church officials with those from the Roman church.