Interesting. I have struggled with the inequities for all my life, but have always tried to say, well they lavished all this money on my brother, and look how he turned out!
But it stings, and always will. The only thing you can do is not take your concept of fairness into the family situation.
Like TooFrugal, I've tried to resolve this internally, as the only thing I do know about these situations is that your parents are blind to the inequity. And that they will hotly deny any insinuation of favoritism. Luckily, I have a sister that also shares the not-favorite title with me, so I do have company.
I have the grim recognition that in the future, when my parents need care and probably money, I will be the one to provide it, as n'er do well bro' will be "short". They've given him money to their own detriment. But one thing I can guarantee is that he'll never see a dime out of me.
Being child-free, I don't have the seething anger that my sister feels when her kids are short-changed on time with the grandparents due to brother's kids always needing a free babysitter.
All I can say, boilerman, is that you are not alone in your resentment, but the healthiest thing you can do is let it go. I am still working on that noble goal, with marginal success.