This is how things usually go:
Couple get married - the man does a reasonably good job of demonstrating that he's housetrained, can brush his teeth, hold down a job and perhaps even work the washing machine. He may even be able to cook a couple of meals. Woman thinks "yeah, he's okay, I can cope with this".
Brief honeymoon period the children start arriving. Man scuttles off to work each day and doesn't really think about what's going on at home ignores his wife's stress. Woman starts to realise that motherhood is actually really hard work, boring and mentally draining especially when junior number two turns up and things get even harder. No family around to ease the burden or offload to. Meanwhile the man expects his wife to return to work to help cover the mortgage and bills, so she ends up with even more to do. The balance tips in completely the wrong direction and his marriage is living on borrowed time now.
The couple potters on like this for a while whilst the resentments and hurt build up. She's always tired, overwhelmed and unfulfilled and he can't understand why she's not the carefree, alluring female he married. He starts to look elsewhere and finds another woman. Wife is dropped in it and finds herself alone with two or three children to deal with, having to support them by herself and hold down a job. She gets angry. Ex husband sees the anger and labels her a 'crazy ex'. Marries woman number two and the cycle starts again.
All because he couldn't be arsed to grow up and take equal responsibility for the children he wanted and helped to produce. If you want to have the privilege of passing your genes on you have to pay the price by putting the work in, not leaving it to someone else.