Good parenting starts with the right choice of a partner. Unfortunately your mother did a poor choice and didn't go away from your farther as soon as it was clear.
Discussion
My mother was extremely ill, her parents were dead, she couldn't work due to health. My father actually tricked my mom into thinking he was amazing. My mother is not responsible for my father's poor choices. Yes she should have chose better, but she watched her parents beat each other and was rapped from the age of 4. It isn't just one thing that should or should not have happened, it was a multitude. Fortunately I chose at 6 to have a different life no matter how hard that road would be. My mom should have left my dad yes, but it isn't her fault my dad sucked. At first my Dad was offering to help with her children which weren't his, RED FLAG to any woman with children who are dating. My mother fell in love with my father when he asked if she had bread and milk for her kids on their 1st or second date. My mom was unfortunately bad with men, but my father also just sucked. However I am thankful for every bad thing that has ever happened to me. It allows me to be a better mom, and made me a better nurse when I was one. I love both of parents still and am thankful for them, I'll do better is all that matters.
Why offering to help with preexisting kids is a red flag? It only tells that the guy has low self esteem, but he doesn't have to be an awful person. And by the way having preexisting kids is even more red flag for a woman on a date, so maybe she thought it is a match of red flags or something 🤔
I'm overly visual, and have been molested as a child. Until a man knows your child and has a relationship it's weird to offer help right off the bat. Predators put themselves in a position to look good and helpful. Now if it's been a while yeah he should want to be a father figure, but right away is weird. Favoritism is also a sign of grooming, so gotta watch for this shit. Especially in our new world, here I'm Canada they are pushing pedophiles are wrongfully judged. There are ads on Facebook saying change the stigma towards pedophiles. I truly believe it is prevalent amongst 50+ % of the population, so as a mom I'm so on guard. I'll die before I ever let it happen to my kids. I'm very thankful I have a good husband, and a good grandma. Children are treasures that have to be protected, and yes I sound crazy but straight up almost everyone I've met has been assaulted as a child or teen. So yeah I thank Jesus for my position in life cause otherwise I'd be having a heart attack.