A complicated relationship

So this isn’t really TMI but I’ve gotten the best advice from this group so far so I figured I’d post it here. A few summers ago I had a fling with a guy. Nothing crazy, we made out a lot and played Minecraft together (I know, simpler times). Him and I hung out today and tonight he texted me saying that he still has feelings for me. I told him I do too. Here’s the catch. I want to start out saying we are NOT related by blood at all. My great aunt is his long term foster mother, making him technically like my second cousin once removed or something like that. I feel weird about liking him, and actually dating would cause some worry in our families, but I really genuinely like him. I really only see him a couple times a year, so it’s not really like we’re family, i don’t even consider us family. It’s also important to note that I did know him before he was taken in by my great aunt, but the fling happened after. He will be 18 soon, so she legally won’t be his guardian anyway. Any advice helps, thanks.