Keeping in mind that I can be a total evil monster...

Be SUPER sweet and thoughtful and considerate toward him. Give him an awesome gift that is really cool that is just the sort of thing he likes (not at the expense of thoughtful gifts for the nice members of your family, mind). When he is a d!ckweed to you anyway, which he will be, don't even let it upset you, remember- he's a mean spirited moron, but be even MORE gracious and considerate. Also, compliment him on the wonderful gifts he gives everyone else, but don't mention your gift to him, or the fact that you have been excluded- others will notice without a word from you.

The trick is to be sweet and gracious, but not in an intimate loving familial way- more like a super well trained customer service representative. The goal is to be super nice without communicating that he actually matters to you. You are just being nice because that is what you are like, whether he deserves it or not.

Now be careful not to be servant like, just be super pleasant to him, without even reacting to his nastiness. Just let it roll off of you while you continue to bond with the rest of your family, who do matter to you. For self preservation purposes, though, I recommend against seeking him out, and not being around him when it is reasonably possible.