That might be fun. Maybe one of his parents also worked at Silph. Or they just knew each other in general living in the same city being the same age.
Well, I was thinking that they at least knew of each other in some capacity. Maybe him aware of Lisette moreso than her aware of him. Saffron is the largest city in Kanto after all. Lisette's little gang of delinquents probably made a few scenes though that would have at least got them some attention from the locals. Vandalizing street signs, breaking and entering, generally making a nuisance of themselves and something a bit...worse, recently.
More to the point, I was thinking that he might be aware of just what exactly her and her little gang did recently that really sorta made people...antsy. Because it's sorta bad. Though her parents and sister, plus the fact she's a minor, managed to keep it on the hushed side of things.
Of course, if you do want them to be friends or maybe even a friendly rivalry or something, that works too. We can work something like that out.