What’s your experience with stepfamilies?

So my 4 year old son hasn’t seen his dad in a year and before that was just once a month. His dads family hasn’t seen him since he was 5 months old.

I have a 2 month old with my now boyfriend and we’re figuring out the whole stepdad thing. He says he’s all in he loves my son like his own…I’ve never forced that on him it was his decision. But now it’s kind of a huge adjustment now that we have a kid together

So I’m curious what’s your experiences with stepdads, stepfamilies… did they welcome your kid into their family, did yous have any trouble adjusting?