I remember seeing a post of yours elsewhere where you mentioned about difficulty mustering the energy and mental strength to go out beyond your home (possibly linked to your parents being quite overprotective? I may be remembering wrong). Regardless of the specifics, I think that factors like that can worsen relations between family members. My brother and I don’t get on well when we’re living in the same house, for instance. That’s made worse by my mom being a difficult person to live with.

But I think you’re right also, that there is a significant component of the grass being greener on the other side. I know plenty of people who are only children, who wish they had siblings, and people with siblings who wish they were an only child.