BG..... it's not your problem that he doesn't know how to take care of "his" son. In my opinion you should not have been there. If she wants him to take care of the little guy, then it is her problem to teach him how, or his problem to find out. It sure as heck isn't you problem.
Actually, turning off your phone wouldn't have been a terrible plan, in my opinion. Let them figure it out.
