Relationships with in-laws and sister-in-laws

by Kari
(US)

In the past, I have only dated men that have sisters or a mix of sisters and brothers. I have had no problem getting along with my boyfriend's parents or siblings. You would think that I would be intimidated by the actual sisters of the man I dated, but we always got along well. With girls, you can just start talking about a pair of shoes or a slight common interest and the conversation just starts right up.
However, the new man I'm dating only has brothers. I have never been in a relationship before with such a male dominant family. I get along well with his parents, but am always nervous about getting along with the brothers. Men can be much more difficult to talk to, particularly, if they only say what's on their mind and don't expand or continue a conversation. Along with the desire for approval by the brothers and getting along with them. I am always lacking confidence and nervous to meet the brothers' girlfriends. I just keep wondering if the family (mother/father/brothers/all of the above) likes them more, or if we will be able to get along, or if I'm not good enough for the family compared to these other girls, or even if I'm pretty enough compared to them. Also, each of the girlfriends are pursuing doctorate degrees (medical doctors) and even though I am too, I feel less important or worthy now that I'm not unique in that regard. Is this just selfish?

I know that I have a lot of good qualities to offer, but this entirely new situation seems to have thrown a wrench in my self-confidence.