My impression was that, that was a grown up X with his kids.

I'd say perhaps, but the story doesn't mention it outright: He COULD be X, but not be, it just isn't mentioned and left up to interpretation

The adult's hairstyle looked like X, and his shirt was also the same color as X's. Maybe its to show that in another life X lived happily and had kids? I know I'm trying to make it seem like something its not but it is possible, since they look similar.