ESH. How the hell did you guys let this boy think you were his father for 7 years? You suck for doing that at a party, your wife sucks for letting him think that and also sending him to you to ask who his dad is (wtf?). You also suck for the comment about your wife keeping her legs closed. You need to get over it and not talk about the life of a child like that.

Also you need to have a talk with your son and explain to him that is still his brother. I’m usually all for anyone getting therapist but in this instance, I don’t see how it’s not your responsibility to fix this. Talk to your son, he’s rejecting his brother because he is mimicking you. If your child is rude to literally anyone, it’s your job to parent them and help them learn that is not okay. Your son will have a hard time in the future if he’s isn’t taught to get along with others and this is the perfect time for you to help him learn this. He clearly looks up to you so you can 100% fix this.