She never did, but when people are comfortable with sexual orientation they generally can use pronouns. The OP cannot.
I am a parent, I get that there are just some circumstances that suck and there are times it is not you , it is the kid. I have one of those kids. I love him to the moon and back, would do anything for him, but Holy Difficult! But he comes to everything. I mean EVERYTHING! Except vacations Then he is very vocal about not joining us. At that point I want to say GOOD! But I don't. So I know it is not always the parents btu in this case, there is a lot more going on.
Two things. My son would never join us on a vacation like this whirlwind Osbourn Lights trip. I cannot even get him to come on a relaxing 6, 7, 8, 9, 10...day trip. Nothing. And he is so socially awkward he tells me exactly why he will not go. I won't leave him and his wife out, but I know he is not joining us. Your trip? I would rather chew glass and die then do that. And I love Disney.
OP- I say this in the kindest way I can. Let this go. Call your son and invite him and his SO for every gathering. If he can come be happy. If he he says he cannot, tell him you will miss him, and will see him when they have time. If he can only come for a few hours, enjoy his visit.
If you all are vacationing, invite them. If they decline be gracious. If they come, treat them the same you treat your other son and his wife.
Whatever you do, stop talking. My husband gave me this advice when my youngest brought home the most awful girl on the face of the Earth. She was the poster child of nasty. He finally told me to stop. Just stop. Not to say one word that was not nice. You do the same, it makes all the difference in theworld