Loneliness Support Group
Loneliness is an emotional state in which a person experiences a powerful feeling of emptiness and isolation. Loneliness is more than the feeling of wanting company or wanting to do something with another person. Loneliness is a feeling of being cut off, disconnected and alienated from other people. The lonely person may find it difficult or even impossible to have any...

I am not sure you should feel like you are being excluded, it may be that your boyfriends family is a little different from the norm.
And as far as family and siblings go reminiscing, I haven't gotten to see much of that either. I would love if they shared stories in front of me but they don't.
I can't believe I am saying this but even my abusive controlling ex who didn't let me hang with my friends and family at least included me with his friends. They shared funny stories and took me places with them and we all would cook or go out or play board games. His friends were great to me. So I know how my current bf and his friends and family are is not normal. I just wish there were more people with positive experience with friends in groups like I had when I was younger.