According to a new study of 13,446 youngsters, only kids do suffer socially — at first. By their teens, everyone's on a level playing field. "Whatever benefits there are in having a sibling are mediated; there's a catch-up."
My experience with only-childhood was much like Florence King's starting kindergarten: "I wasn't used to children, and they were getting on my nerves. Whose, it appeared that I was a child, too. I hadn't known that before; I thought I was just short."
Fortunately my parents had the foresight to divorce and provide me with steps and halves that I couldn't imagine life without. So I—only child of divorced parents—got the best of both worlds, not social incompetence. :)