Family Issues Support Group
Family issues is a huge range that go from minor conflict to major misbehaviour and even abuse on the part of individual members of the family occur. Whether you feel you are in a dysfunctional family or you're dealing with a very specific issue, this is the place to talk about it and find others who might be going through the same thing.
Could it be that they are having troubles accepting your GLBT lifestyle?
I'd come up with some objective 'proof' that they are treating you unfairly. Don't put them on the defensive, or it'll erupt into an argument.
Just say that you don't feel as close as your siblings and you'd like that to change for the better. Who could argue with that, right???