They were the sisters of Henry VIII. The eldest married the King of Scotland, and was the ancestress of James VI and I two ways; the youngest married the King of France, but that only lasted a few months because he was old and fat and died soon. She then married the Duke of Suffolk, for love.
It was a fascinating book, by Maria Perry. Eminently readable, going chapter for chapter with the two lives in parallel. I must say I was a bit disappointed with how much emphasis was put on H VIII and his court; I know this makes sense, because what happened to Margaret in particular had a lot to do with it, but still it did not concentrate on them exclusively as much as I had hoped. Still, I learnt a lot, and I enjoyed it greatly.