New girlfriend's ex is hanging around us like a bad smell

I'm a man in my early-30s and I've been dating my girlfriend for a few months. We have a lot of shared interests and things have already got pretty serious between us.

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When we first met, we had both recently come out of relationships. I was with my ex for 18 months and we're not in contact at all. But my girlfriend was with her ex for seven years and they met at 21, and he's still very much part of her life.

I get that they were each other's first proper relationship and that they were together for a long time but, for me, he's just too cosy with my girlfriend and her family. He's also single, which bugs me too. It's not like my girlfriend sees him on her own, but they still speak quite a lot and he drops in on her parents fairly regularly.