DH is the middle child in his family, and is definitely the 'forgotten' one - firstborn is the favourite son, can do no wrong, and #3 is the baby sister who gets everything she wants but DH always had to fend for himself. His mum put both of the others through uni, but never even gave him bus money etc etc.

Of course you can control it, you choose how you parent and being conscious of it is often enough to make it not happen. I think, as with anything, it is what you make it.