Why do your parents care about your adult girl siblings more than you if you are an adult guy?

Well, Girls enjoy being the center of attention and causing drama and that kind of stuff.

And Adult Guys Are Laid Back And Aren't worried about that Subject

Sometimes Girls just get mad easily and when their mad, THIER MAD!

So that's why It seems your parents care about your adult girl siblings than adult guys.

Another point of view:

There's not enough information here to make an accurate diagnosis. The exact ages, the relative ages and the birth order are relevant here. So is marital status, career status and a great many other variables. Many people mistake an imbalance in attention for lack of caring. If what you suspect is actually true, you won't change that. But part of being an adult is learning to alter your expectations. Congratulate yourself on your self-reliance and look for nurturing elsewhere.