I met my now wife when I had just begun physical transition. At that stage, I was still getting misgendered occasionally (although I had been living as male for a while) and I was much more open about my situation, because I felt I owed an explanation to those around me.
So they know, and always have. It’s been a blessing, to be honest – they’re wonderfully supportive and certainly don’t see me as less of a Father to thier Grandson, or less of a man in general due to it. They were of course trepidatious at first, but I feel that was more due to me being a new presence in thier Daughter’s life than me happening to have been born female.
My Father-in-Law literally tells me that I’m his “Favorite Son-in-Law”, and my Mother-in-Law approves greatly of our Marriage.
So I guess my situation is different, but if they can see how thier Daughter feels about you – and you give them no reason to doubt your integrity; there’s nothing stopping you from marrying the Woman you love.
You don’t have to tell them about your history, you don’t owe anyone anything. This is your private life, and you get to choose who, when, how and if that information is shared. Good luck man.