Here is what the Foundation of Medieval Genealogy has to say about her: [SIBYLLA], [cousin of SIWARD Earl of Northumbria, daughter of ---]. The Chronicle of John of Fordun records that the mother of Malcolm and Donald Bane, Duncan’s sons, was "the cousin of Earl Siward". This information is not included in any earlier source and should be considered dubious. In one earlier king list, King Malcolm III's mother is named "Suthen". No reference has been found in primary sources to her being named Sibylla, the name found in many secondary sources.
With her parents unknown I don't believe she can accurately be described as someones daughter which rules out three of the choices. The geographic doesn't really do anything as it applies to her cousin and not her so I would also eliminate those. That sort of just leaves "Unknown". Then there is the question of her first name "Sybil", "Suthen" or "Sibylla"?
If she was my ancestor and I was creating a profile for her in my personal genealogy program - I wouldn't! There isn't enough known about her. I think there should be a paragraph/section referring to her in her husband's profile that explains the little that is known about her and the theories around her name.
Sybil (Siwardsdatter)
Sybilla B. (Bjornsdatter)
Sybill (Northumberland)
Suthen (Siwardsdottir)
Sybilla (Uknown)
Sybill (Northumbria)
