marriage has always been recognised as the best way of bringing up children.

In Victorian times, when most children were born in wedlock, the incidence of child abuse was far higher than it is now. In fact, you don't need to go that far back to see the same statistics. Abused children from bad parents in bad marriages are probably in a higher percentage than children born to people who stay with each other of of love rather than because of a piece of paper or few words mumbled by a vicar. Rose coloured specs I'm afraid.