Remember that time when Julian thought that his great-grandmother might have served aboard the Enterprise? Well I am 1701% sure that this was his great-grandfather.
My headcanon about this is that while, obviously, Julian is not his own great-grandfather, his great-grandparents met because of him. Lieutenant Watley was indeed charmed by this lovely dork she saw briefly in the turbolift, and goes looking for him later. She thinks she’s found him, but wait… no, it’s not the same man, is it? Then this guy sees her staring at him, and his face lights up in a huge, goofy grin. Lieutenant Watley blinks a bit. It is him. Surely there can’t be two grins in the galaxy like that. She’d thought for a second… but, after all, she had only seen him for a moment in the turbolift…
She goes to say hello, she’s glad to see him again, and he doesn’t want to admit he can’t remember meeting her before, so he plays along, and they end up talking about science for hours, and he’s late for his next duty shift and his workmates tease him about it, but he’s walking on air anyway, because she asked him to dinner, and the rest is history.
CAN I ACCEPT THIS HEADCANON MORE THAN ONCE? I ACCEPT IT A MILLION TIMES OVER!!!