Wasn't trying to be goady, but trying to counterbalance the "nothing to see here" levels of denial on this thread.
My mum was an only and absolutely hated it. Longed for a sibling, was lonely and talked about it a lot as an adult.
My brother and wife have had an only through choice -- wife basically made the decision. Their DD absolutely lives up to the little emperor syndrome. Really, really can't share, absolutely expects to get her own way all the time. Very intense atmosphere at home , not in a good way.
Most of my friends have siblings; one or two are onlies so I definitely don't have an irrational hatred of onlies. But I've come across a few people over the years where I can tell they are onlies and I've been proved right.
I do of course know some onlies who don't fit the stereotype. I typed hastily earlier and I'm sorry for the patronising and offensive comment.
Put more positively and tactfully, my overall point is that there are definite pitfalls to having an only, and lots of advantages to having more than one. Not just for the child(ren) but also for you as parents. And it's something that changes with time. My dc are now getting on in different ways now that they are adults/nearly adults.
I get on differently with my own siblings than I did as a child. I absolutely couldn't imagine life without them. They are a gift to me and I'm trying, clumsily and tactlessly, to get that message across.