Most Helpful Guy
it's the mother of his child. so that factors in I'm sure. Your bf's mom probably understands the importance of that nuclear family dynamic. Additionally the ex (sort of that Neil Armstrong on teh moon effect) planted her flag first. So there is a special spot reserved for her, despite the fact that there were 3 other people who traveled to the moon since Neil Armstrong opened the door, planted the flag, bla bla he is revered in history.
I think you just try not to let it bother you. The more it irks you the more it probably affects your behavior which may be apparent to the mom. If everyone else in his family likes you then it is clear that the mom is in the minority and will have to come around or be left in the dust... especially since her son is with you and after 4 years doesn't' seem to be making any other plans any time soon0