Phillppa Gregory has written The Other Queen, due out next Spring, which tells the story of Mary Queen of Scots, and after that she is doing a series of three on the Wars of the Roses. I don't know if I'm pleased or quaking in my boots, for each Gregory book I've read contains incest and I'm not at all sure I want to read that Richard III or Mary indulged in such practices!
Come to think of it, Mary was an only child, so there cannot be any mileage there, but she did have several Guise uncles in a handy position at the French court. As for Richard, I can't recall if he had sisters but since the Rose of Raby had seven surviving children and I can only remember four sons, (Edward, Edmund and George, plus Richard) I guess he did.
One reassuring thing about it is that the Tudor thing is set to go on for a little while longer as far as fiction novels are concerned. That makes me feel more secure in my choice of that time for the next work...with which I must get to grips very soon. For this time period, the danger is that there is so much to read one can get lost in the research and never start writing!