I have 2 DDs. We are toying with the idea of a third baby. I've always been acutely aware of middle child syndrome, and several friends who are one of three often mention it too and it seems to be more prevalent when it's three siblings of the same sex.
I hate the idea of my DD2 becoming the stereotypical attention-seeking / difficult / awkward / etc middle sister if we were to have another girl. If we had a boy then I think each of them would have their own role/place a bit more.
I suspect this is just one of those odd things that is only a thing in my head and no one else's, but it's really bugging me as it's pretty much the only thing stopping me from seriously thinking about TTC #3.......