It seems that a popular choice for Edward is Mary Queen of Scots. But idk if her mother would have agreed to such a match, ever. She was French and catholic, and a marriage with England, while good for Edward, wouldn't have necessarily looked as good for Mary, given the two countries historical animosity. I think it's likely she marries Francis Ii, who still dies in 1560, and that she remarries to Lord Darnley. My only hope is that her second husband act better than he did iotl. Currently, I have her having three children with him, James b. 1566, Alexander, b. 1569, and Margaret, b. 1571. Idk if a divorce with Darnley is possible since they are catholic, but would it be necessary? He certainly wasn't a very good husband, but would he mellow out with age, or always be a nuisance?