We've been together for 5 years, he has a difficult relationship with his 2 daughters now 22 and 17 they don't see each other often there are no boundaries and little respect. I met them a year into relationship, we got on OK but they do lack manners and don't get my humour. We arranged to spend Xmas 2017 at my house 2 days before they told him they wanted it to be just them 3 at his flat. He didn't say no and it was really awkward in the end I called their bluff and they all came to mine as planned. The year after we arranged between Xmas and New year same thing happened I told him to go be at flat with them he did but wasn't happy. The Xmas after same sort of thing but she kicked off at me via text when I asked her if they were still staying boxing day. Apparently it was not my Xmas but theirs and I should mind my own business. Then she went to bf and told him I was being mean and sent him the texts. He told her it wasn't her fault but mine. He didn't believe this but he says anything to please them and obviously this does not help such situations. She refused to talk to me to sort it out, then bf said she had given him an ultimatum and he'd chosen me. She didn't come Xmas but the younger one did and didn't speak 2 words to me. It was all so awkward and I felt uncomfortable in my own home. New years eve11.30 they rang him shouting and hollering and referred to me as that thing you call a gf - he didn't defend me. New year I found out that he'd told her it wasn't her fault and that the ultimatum was actually an alternate arrangement that still included me. He had told all his family that she'd made him choose and was slagging her off too every one for not apologising to me. I couldn't make him understand that what he had told her made the situation worse why not be honest. 2 years on I have not spoken or seen either of them. My problem is he is now expecting this to be sorted out so we can spend Xmas together. He's said several times over 2 years he was gonna sort it out but didn't. I feel I'm in a no win situation. If we sit down and thrash this out the truth will come out that her dad lied to and about her for 2 years - this will possibly ruin their relationship or i suck it up forget it and move on but obviously I've got to put up with the drama and rejection name calling and nasty mess from them knowing he won't have my back. I don't want to have that every year its stressful and I'd rather spend Xmas with nice people or even on my own. He blames her yet as much as I try he will not own the fact that his actions has got us in this situation and that by me having nothing to do with his kids I'm actually having His back and keeping their relationship in tact.
Should I stick to my guns and stay away from them and keep the truth under my hat? We don't live together and they have spent time at my house over the 3 years on other occasions when it seemed to suit them.