People who never had real parents tend to parentify their children. This doesn't just mean that they want their children to take care of them emotionally (and sometimes physically) the way their parents should have.
This is common, but there are other ways to parentify and mess up your kids.
You can treat them like your messed up parents wanted to be treated, thinking misguidedly that this is simply the best way to treat human beings.
You can try to do anything not to upset them. You can try to leave every decision up to them. You can allow them to walk all over you (sometimes literally) thinking it's your duty to just bear it. You can fail to have any boundaries. You can treat their every wish as your command.
I've been guilty of this. And then I've sometimes snapped and said "What do you want from me?"
Authoritarianism and permissiveness are two sides of the same coin - a parent who doesn't instinctively feel where sane boundaries lie because his or hers were violated in childhood.
Sometimes even infantilization is actually a form of parentification. My father did many age-inappropriate things for me and sometimes behaved as if I were a princess and he were my servant (but there was sarcasm involved). For instance, he'd ask me if I wanted something to eat in my room, I'd say "OK", he'd bring it to me and I'd finish it and then go on reading or whatever. He'd come in, see the empty plate, and sardonically say "May I remove Your plate now, your Majesty?" or something like that. There was no right response. He was resentful about doing something I never asked him to do. I'd mumble "Yes" or try to take the plate back myself - he'd never let me.
He and his sister had to serve their narcissistic mother as the Queen she was. So he did the same for me, because I represented her somehow. She demanded this sort of treatment, I never did, I was deeply embarrassed by it.
I'm a bit down now and feel like whatever I do with my kids, it will somehow be wrong because I'm broken and can't get it just right. I'll just do the opposite of what my parents did, and the cycle will go on.