Dating guys with kids! HELPP! WHAT SHOLD I DO?!

So in my previous post I posted about my friend who's 24 and he has a son. I don't think that there's nothing wrong with that at all. I just think that I'm not ready to meet his son when the time comes. Me and this guy aren't even dating just yet but we're seeing each other casually.

Now his son is old enough to be my nephew (he's 7. my nephew is turning 5 this year). He's told me some stuff bout him like you know " yeah me and his mother didn't work out and we don't have a good relationship but we co-parent".

I'm really good with younger kids I didn't grow up with any younger siblings but I have two older sisters (like he did) and I feel like I am might get attached but I don't want to get attached because I know he is a good dad to his son and that he really loves and misses him.

I'm only 21 I don't want to feel like i'm going to replace his mom even know me and a guy aren't serious just yet maybe I'm overthinking this any advice? Also me and him have slept together twice (with an condom and I'm on birth control) I just don't want to have any oops ifyaknowwhatimean