Emptiness at family functions

I wonder if anyone feels this way, but growing up I always felt so alone at family parties and at holidays when everyone is talking to siblings and has a lot of immediate family, and now it’s just my mom and I. I have cousins I am close with, but this is something on a deeper level I feel that I can’t explain and I have always felt it. It’s just a hole that can’t be filled and it sucks so bad. I want siblings to feel close to, and knowing I will never have that makes me feel so down at times. Watching everyone interact with their siblings and feeling like an outsider even though it’s family.