Only children dating relationships how to not be intimidating
This has more to do with what kind of family you see yourself becoming a part of rather than if this is an only child thing.
It'll never change, or at least never change the way you want it to. Did you ever wonder if they are "not nice" to you because you're distant, cold and unmotivated to be involved with them?
So, I can understand how relationships can be affected by their birth order (or lack of).
I am 1 of 3 and I love big families, I love family functions etc.
Your SO seems to like his family and spending time with them.
He's used to the "business" that seems to be going on with a larger family.