Is it normal that I feel uncomfortable being around my boyfriends family?

weI met his family before. He always inviting me to hang out with them. But for some reason i don't feel comfortable. When i met them they wasn't mean or rude or anything. I kinda feel bad he invites me over or somewhere with them and i don't go because he has a large family and is close with them. I love him to death. I don't know why because im am not shy unless its around people i don't know very well. Am i horrible girlfriend for this?