My boyfriend is 11 years older then me and his friends don't like me becaues of this, what can I do?

I'm 19 and my boyfriend of 6 months now is 31. One of his friends likes me and the other is polite, but the rest of his friends don't like me because I'm so young. When we go out they always make remarks like "go take care of your kid" or "oh, you didn't have to babysit tonight". I told him to spend more time with them, but he doesn't want to because he hates the remarks they make about me. I don't want to be the reason he loses his friends, and one day him blame me for it. I just don't know why his friends can't be friends and be happy for him. What can I do to get his friends to like me, or at least grow up a bit?
My boyfriend is 11 years older then me and his friends don't like me becaues of this, what can I do?
Post Opinion