The joke's on you!
I don't even know where Rosebud the sled is from! *evil cackle*
But seriously though, since you haven't actually divulged why they are TECHNICALLY the same person, I am just going to watch Fate/Stay now until I figure it out. I'll get back to you later.
And I'll be ready to spoiler-duel you with gunblade knuckleduster card game monsters.