*hugs* It's normal Justfloating, very normal to care so much about your family members. As to it affecting you so much as to start a depression, that's normal too, at least for me. I had a very difficult time when my parents separated almost 7 years ago. I was angry and upset and guilty for feeling that way since I still loved both of them. Even the suffering of people I don't know can sometimes start a depression for me, but I'm a very empathetic person.

As for your Aunt, give her all the love and support you can. With what she's going through it sounds like she'll need a shoulder to cry on, or even cry with her. For the situation with your grandfather it sounds like you're confused as to whether or not you'll forgive him. He is your grandfather and you will always love him. I'd suggest looking at the person he is now and asking your grandmother if she's happy with him now.
Those are just my opinions and suggestions. I can't say that I have much experience in this area, but I hope it helps. =)