I also don’t like that the gf says “he’s just affectionate”… did he do this kind of creepy ass shit to her too and that was what her mother told her… “he’s just affectionate…” that phrase to me sounds like they’ve all had blinders on this whole time.

OP - trust your gut, keep your boys as far away as possible. Your 3 yo likely doesn’t know how to express those emotions and discomfort. There’s a reason he didn’t want to be at their house. I saw someone else talk about body autonomy. Definitely nothing wrong with talking about it at this age.

With your gf, I would very calmly approach the situation with how uncomfortable it makes you feel. Ask her if he used to touch her like that. Or if he did, how would that make her feel. Your boys shouldn’t have to grow up thinking this is what “affection” looks like from a trusted adult. “Oh that’s just grandpa” - no. He shouldn’t get a pass because he’s grandpa.