Depends on where you’re from.
The majority of young (ie under 40) couples in the UK are unmarried – many of them parents.
Same in many other parts of Northern Europe – Germany, the Netherlands, Scandanavia, even parts of France, Italy and Spain which are traditionally Roman Catholic.
So far, society has not fallen apart….
Having a piece of paper saying you’re married isn’t going to make you love and care for your children any better than not having the piece of paper. If you’re going to be a crap parent, then even being married by the Pope himself is not going to make you better at it.
Conversely, you can be a good parent, whether or not you’re married.