He always hates that he compares Jubilee to Katherine by thinking 'One of the girls Wolverine had adopted that I apparently have too' because Jubilee isn't a "replacement" Katherine, but there's a similar line to how they became close.

In some ways, Jubilee reminds him of himself, before he fled Germany, and he wonders how much is what her natal personality is, how much is a reaction to all the shit being a Mutant makes you go through, and how much is a reaction to all the shit being an X-Men puts you through. There are times she'll say or do something that will make him grit his teeth and walk away, because shouting won't help. Not that he won't shout at times. Not that there aren't others when she makes him laugh in delight.

She's probably the grandchild he has the closest relationship to, the one that despite not being a teenager has taught him the most - even more than the New Mutants - how to deal with them. He's found he has more patience for those he loves than he thought he did, more ability to love and open up than he thought he did and as much as he is grateful for that, it scares him too. A lot. Jubilee is a huge chink in his emotional armor and he's waiting for the day someone tries to use that against him, because he's certain that will happen.

He's very sure she won't up and leave him, but not completely sure and that scares him too.

But what scared him most was nearly losing her.