Dicking about with the family tree produced some results that, whilst groovy if true, I completely do not believe. I rather suspect someone got their facts seriously wrong somewhere along the line. It is a good thing I found this out before I decided to go and rub potential Vikings in
dethorats' face.
However, I can say this with a reasonable amount of confidence:
Y'are a baggage, the Slys are no rogues. Look in the chronicles; we came in with Richard Conqueror.
Still pretty groovy. :D