My DS (35) has had a few long-term relationships, but never married. I get the feeling this one might be "the one". Because he's always had different girls hanging around when my DD had her baby she didn't feel comfortable with the constant changing of arm candy. As such we stopped inviting them all round together. He may or may not turn up to ours with a girlfriend, so we just wouldn't invite them at the same time.
He phones regularly, but we don't see him much now to be honest. When we speak I ask what he's up to and he'll mention going out with his GF's mum or meeting up with her and her sisters for an outing. I have mentioned to him that we'd like to meet her, but he keeps batting away the suggestions.
I know he knows that his sister is the reason he stopped being invited to Sunday lunch and things, I did agree with his sister, that explaining the changing of companions was awkward with a small child, which is why I allowed it. But now, this girl has been 2 years, and he is very much involved with her family. I feel like I've broken something and have no idea how to fix it.