Hailey
With the way things happen here, he could be from a completely different timeline than you. It's even possible that he wasn't even going to have Hope in the timeline that he's from. I know that things are already a lot different for me. Honestly, I'd just tell him. He's been here long enough to know how things can be. On the other hand, Kevin's head is still spinning.
Jack just calls me Kate. The age thing just makes "mom" weird for both of us.