Same here, Rose. When younger it didn't bother me so much but in later years, when I see how close our kids have remained and the things that they do together, I regret what I must have missed.I never had any.
For those who did have siblings but not in a pleasant way, I do feel truly sorry. They've had it tougher than those of us without. My wife had one sister (who passed away a a relatively young age -51) and there's wasn't a pleasant relationship. My wife has always been saddened by it but has remained close to her sister's children and them to her.