Through my experiences with my 4 children as I've watched them growin' up -- they learned alot about their parents by watchin' them. They will NOT forget that easy when they remember things while growin' up. They will start askin' questions their divorced parents about why mother or father do this or do that... and, even they will defend their mother or father who ever is more innocent, that's IF either mother or father NEVER mentions bad things about their spouse to their kids.
All my 4 children accused their father when they were in their teen ages, because they kept hearin' their father sayin' bad things about their biological mother ... or let's say their father's girlfriend talk bad things about their biological mother, just because their father said alot of things to their father's girlfriend. What their father and father's girlfriend did NOT know about is that I've NEVER mentioned bad things to my kids about their father/father's girlfriend for years until my kids reached the ages of 18.
All my 4 children are now realized that their biological mother ( me ) is a good mom. I don't drink nor smoke ( pot ) nor gamble nor do drugs - NADA. I was very straight clean, except for that ciggie until 2 years ago I quit.
Children can watch their parents on both sides while growin' up. They could even question their parents to find out the truth. They will keep their mind what their parents told them about each other. Let me tell you - children are NOT that stupid nowsdays about the family matter.
I would advice for girlfriends/boyfriends to keep mind their own business and let the biological parents work things out themselves with their kids. NEVER butt in. No 3rd party involves, either.... because, if you do - children will hate you for screwin' their parents' friendship for children's sake.
Never make children to call girlfriend " Mommy " or boyfriend " Daddy ". They only have ONE biological mother and ONE biological father who they were born from.... their real blood and flesh parents, NOT girlfriend or boyfriend.
And, also -- girlfriends/boyfriends have to learn to respect children's biological parents and let them be what ever they want for the sake of friendship --- because, the word " divorce " or " break up " hurt them enough. It's their parents' responsibility to see that their children are happy WITHOUT bringin' " past " in their lives ( bad things or dwell on things ).