Lost case to be a rebound girl??

Hey everyone, hope you all having a great day!

I just need a feedback/advice on my current situation... I’ll try to keep it short hahaha.

I’m a 21 yo and I live with two of my best friends (couple). My friends best friend just got out of 5 years relationships and he is heartbroken and stuff (it only happened 4 weeks ago)... he was hanging out with us for a bit. And we started seeing each other for like 3 weeks now, I never met him while he was in previous relationships. my friends told me not to have any affairs with him... but know they know and we had kind of a fight about it since we didn’t tell them about us seeing each other, even though i thought it was obvious and wouldn’t be such a drama...

anyway, he is heartbroken after his relationships and I’m kind of rebound girl I suppose. The scariest part is that he is 35 and has a 11 yo son... I have no idea what we are doing, but I do feel really calm and comfortable with him, and as he says that’s the way he feels with me too... what should I do, just see where time takes us?? Do you think it can end up good between us??