My parents divorced when I was 30. That was about 25 years too late. When I was 5, they separated briefly and I was very excited at the notion that they would stay separated. (Keep in mind this was in the early 60s, when divorce was uncommon.) Sadly for us all, they reconciled then. Again about 15 years later. Again a few years after that, then a few more deeply unhappy years until my mother finally came to her senses and left my father. My mother never dated again -- she wanted no more compromises and no more drama. She liked men, just didn't ever want to be joined to one. My father immediately started dating a woman who looked just like my mother and dated her until she broke it off when he wouldn't get an annulment so they could get married in the Catholic Church. In reality my father had no interest in marrying again and spent the ten years after their divorce and before their deaths battling my mother in divorce court over property settlement issues (which I dealt with after my mother unexpectedly died and my father rued the day I took over that battle).
Very similar story with my ILs only they never did divorce, never separated, but had a
very dysfunctional relationship as well right up until the moment my MIL died. (I honestly think she was a sociopath.) FIL got remarried with 15 months to a real winner of a woman.
In both cases, the couples got married young in order to have sex. Young lust is not a useful indicator of long-term compatability or emotional health. Not that old lust is either -- my FIL married his 2nd wife because he thought she was hot to trot. (Seriously. Just sleep with people, don't marry them for sex!)
Now, my paternal grandparents had a very unhappy marriage -- also created out of young lust. When my grandmother died, my grandfather remarried a woman with whom he was much more compatible and they were happily married well into their nineties.
Interestingly enough, the best description of my maternal grandparents' marriage came from my paternal grandfather at the funeral of my maternal grandmother. He told me, "I can remember 50 years ago seeing your grandparents walking down Main Street, holding hands and talking to each other a mile a minute. 50 years later, they were still walking down Main Street, holding hands and talking to each other a mile a minute. They were still in love with each other, still enjoyed each other's company. They were very lucky. I envied them." It is definitely that relationship that I use as a model for my own.
My mother never got over her anger at my dad. She eventually married a wonderful man who she made to pay for the sins of my father until the day he died. To this day, and she's 76, she hates my dad and will take any opportunity to make a snarky remark about it. To my dad's credit, I never heard him say ANYTHING negative about my mother. 
because if this I have not been talking to him.
