I think my mum cares for us all equally, but she was always a bit disconnected from me and my brother because she probably thought she had little to teach us and few common interests. So when my sisters came along and turned out a lot like her I think she felt more in touch with them. She's as much of a mum to all of us, but I guess she's better "friends" with my sisters.
My dad is kind of hard to read on that and I don't think he has a clear-cut favourite - but if anyone is, it's me. Again, it would simply be because I turned out so much more like him than any of my siblings, and I think he's always seen me as the intellectual and mature one, even though the oldest of my younger sisters is just like me in that aspect. She's a few years behind, but we're practically the same when it comes to personality and behaviour. Ah well.