So yes, Seymour dominating the early regency for Edward VI, would he propose this marriage? Or would that be Dudley?
Which one is closest to (and being pressured by) Henry/Frances Grey? Though it's worth noting that Henry might be less influential ITTL if butterflies keep one or both of Charles Brandon's sons by Catherine Willoughby alive and prevent the Greys getting the Dukedom of Suffolk.
Given the above (theoretical) for the Scottish line, Edward VI will wed Jane Grey (b fall 1536 or spring 1537) on his fourteenth birthday (12 Oct 1551), with Jane giving birth to Edward, Prince of Wales on 1 Nov 1552; Edward's fatal illness - because of his wife's loving care, is delayed until March 1554, with him dying in the fall of that year. By then, however, Jane has given birth to Henry, Duke of York (10 Sep 1553) and Jane, Princess Royal (9 August 1554). Now we have a King born in lawful matrimony who is the son of Henry VIII's indisputably legal wife Jane *nee Seymour*. And a regency.
How robust was Jane's health? Because giving birth to her first kid at 15, and then two more in the following two years, could kill her.
Would Henry Grey be a shoe-in for the regency, as the kid's grandfather? Presumably with Dudley nearby.
It's kinda irrelevant to the issue at hand, but how does being aunts to the king as well as 4/5/6/7th in the line of succession (depending on how you want to count Mary and Elizabeth) affect the marital prospects of the younger Grey sisters (keeping in mind Mary Grey is still a hunchback)?
I presume no Queen Mary means Norfolk dies in the Tower? Does Courtenay stay in there too?