What would Killy do if he was dating Stoom, but his wife was still alive?
Sorry, I had to! XD
Serious answer: Wow, it’d certainly be an awkward situation that would require a lot of communication between them all. x_x Killy would have wanted his wife to be in his life, but the fact remains that he doesn’t remember her, nor know her at all thus there’s no way they could pick it up where it was left off- Killy absolutely would not be comfortable with that. While there’s sure to be some similarities in his personality, he’s not the same person he was then. I think that both of them would understand that and take it from ground zero without any expectations of it turning romantic again. And hey, he was dead long enough that she probably moved on long ago as well.
Stoom would be quietly seething over the whole thing, as she can have a jealous streak but she’s not so much of a bitch to forbid it. It certainly would put a big strain on the relationship, but ultimately Killy would not leave her even for a person of importance for a life that ended long ago.