I'm married.
I believe that there is a stronger likelihood that co-habiting rather than married couples with children will split up.
I think that's multi-factorial; other posters have suggested some of these factors.
It's just I don't, and never will, believe that a woman should do anything "for her children".
I think all this talk of "supporting families" is another attack on single parents, the majority of whom are female, by another name.
There is a strong correlation between lone parents and benefits; a lot of lone parents are in receipt of benefits. Most women are economically sh*fted when they leave a marriage/relationship. That, too, is multi-factorial. But the fact that they have had dc is a huge factor in that. Work+dc is a gendered experience. Women tend to find their careers impaired after dc. That means, when they leave a relationship/marriage, they are more likely to be in need of state assistance.
This is a return to cutting the benefits budget, at the expense of women and children, done by stealth. It's not quite as obvious as "we're going to make it less attractive to take the option of sitting on your bum , on the dole, surrounded by you profuse offspring. We're going to dis-incentivise being a lone parent." But it's the same thing, by stealth.
Seriously, if a marriage/relationship is great, why would you need to pay the woman to stay in it, and (relationally,) economically penalise her for leaving?