I always thought that she looked like a battered woman. Probably because I had a similar look at times. And that he had absolute control over her and everything else - like 'you will wash that toy or I'll throw it away', 'you will go out and see people whilst I am playing tennis', 'you will do x and y'. I even experienced something similar from that ex when I had a baby and refused to leave said baby unattended and go to the pub next door on holiday 'NORMAL families do this, it's closer than if we were down the end of my parents' garden. WHY DO YOU ALWAYS HAVE TO RUIN THINGS' [slam, crash, things get thrown around, etc, etc]. Naturally, after leaving the piece of tit, there was the YOU'RE NEGLECTING MY CHILD AND DON'T DESERVE TO CALL YOURSELF A MOTHER because I took a bin bag all of five foot out of the front door whilst she was in her cot... Anyhow, abusive men do make a point of crossing all boundaries to show their dominance/control. Making somebody cover up for them because 'nobody will ever believe you, I'll tell them that you did it and you'll lose the other kids too' wouldn't be a particularly unusual act.
It wasn't normal then and it wasn't normal 20 years earlier, either. I do remember that I couldn't get sold Phenergan or Piriton liquid for my allergies around this time as I had the baby in the pushchair in the chemist, though. And there were an awful lot of toddlers/preschoolers spark out sleeping in buggies in the school playground of an afternoon...
Maybe in years to come, the younger siblings will have something to say about how they grew up. Teenagers do have that habit of opening their mouths and letting words just fall out, after all.