He entrenched his position in northern England by marrying Ælfflæd, the daughter of Ealdred, Earl of Bamburgh.
One of Siward's sons is known to have survived him, Waltheof, whose mother was Ælfflæd. Waltheof later rose to be an earl in the East Midlands before becoming Earl of Northumbria.[119] When Waltheof rebelled against William the Conqueror, however, the act led to his execution and to his subsequent veneration as a saint at Crowland Abbey.[120] Waltheof's daughter married David I, King of the Scots, and through this connection Siward became one of the many ancestors of the later Scottish and British monarchs.
