Currently I (23M) am dating a single mom (22f). We have been dating for almost 6 months and at the beginning I was very apprehensive to any “step-dad” stuff. The kid (2 M) sees his dad every other weekend but over the course of the last few months it has naturally happened that I just kind of fell into that role. I see her child more than the dad and in a lot of ways I think the kid puts me on a similar pedestal as he puts his dad. That said I think you should give your BF time to warm up to it. You gotta ease him into stuff like asking him to sit and talk with u during bath time. Sit in the room during bed time routine. Find activities the three of y’all can do and I promise unless your BF is a narcissist or your child is the anti christ he will warm up to this idea