I'm not one to do the math (must be together X years) or make arbitrary rules (must live together/be engaged/be married) about social units. Bagman and I have been together for many years, although we don't live together, and our friends and his siblings invite us to events as a couple.
However, he spends Thanksgiving and Christmas with his ex's family, because that's where his daughters and granddaughter spend it (ex's mom is their last surviving grandparent), and I don't go along because even though I get along well with his ex, and I'm Facebook friends with her sister, it would be awkward. I spend those days with friends, and enjoy the heck out of them.
I think Larry would have the right to be miffed if he was living with his girlfriend, and she was excluded while live-in SO's of other cousins weren't. However, that doesn't seem to be the case. Aunt made a rule, and he decided on his own that he should be the exception to that rule. Not cool.