Relationship problems

So I need advice. I'm 20 and my bf is 25. He was in a relationship about two years ago that resulted in a child. There is nothing wrong with that. However I feel like every time I see the child I see her mom and the mom is not good as a person which results in a bad child. I love my man to death but I feel him having a child bothers me so much I can't be a gf or even a role model for the kid. Any advice on what to do?