I have a half brother and half sister that I grew up with until I was about 12 and my parents split up. I stay in contact with my sister, but we're not very close and while I've tried to contact my brother, but he's never been a 'family' type, so not much to say there.
I will say, growing up with them always sucked because I'm the baby and they always picked on me, but I kind of like the idea of being a lonely child as well. I guess I got to live in both worlds for a bit, but I'm content with how things are, I've nevr needed much family.