Siward Biornsson, Earl of Northumbria - Siward and Suthen/Sybil (wife of Duncan)

Suthen is supposed to be a cousin of Siward. If this is true, the Geni pages would be incorrect because they are showing that Siward was the brother of Suthen's father, which would make Siward her uncle. It also seems odd that Siward's supposed father would be born roughly 57 years before he was. I am wondering if the Bjorn listed as Siward's father on here is possibly his grandfather, not his father. The dates would make more sense as would the relationship of Siward and Suthen being cousins, not uncle and niece.

I am trying to find information to sort this out. Hoping someone can help with this. Thanks!