Well my BIL is on his 3rd marriage and SIL is on her 2nd. I thought that dh was the one sibling who escaped the damage, but here we are, 25 years of marriage and 30 years of being together later. Nobody in my family is divorced except for my brother (and I think his ex is bipolar and actually her parents are divorced. This stuff is contagious).
It's funny, I keep going back to the time when we first got together and dh told me all about his mum leaving and how dreadfully she did it, he told me I was the first person he could trust for a long time, and he spent a lot of time telling me all about it. And he's told me over the years as well. And I feel like it's finally caught up with him never having dealt with it. I feel like ds1 hit the age that dh was when his mum started having affairs and stuff and dh started losing it. I never realised until recently how much it affected him. And I have a lot more empathy for dh now, having experienced abandonment myself. It's awful. It's the worst feeling ever. No wonder he feels so traumatised.
Anyway, sorry to hijack, just kind of thinking aloud here. Maybe if they repeat the cycle and they are blind to it, it's because it's too painful to look at the past directly? It is so hard to have any empathy for the MLC spouse but I am really trying.
Anyway, I hope things are going ok. It does get easier, I don't think anyone can stand that level of pain for too long. Keep putting one foot in front of another and working on yourself and your role in the marrige and at least you'll come out of it all a better person. There has to be some benefit out of this utter misery, right?