((Charmane))
It is hard for me to relate to your experience with your eldest son. I can understand, as a mother myself, how painful and frustrating it must be for you and other family members to see this happening. My children are still very young though ~7 and 5 years.
I have struggled with major depression a few times in my life, so it's difficult for me not to take your son's depression into consideration. There are physical changes within the brain when depression strikes. The changes have been scientifically studied for several years. The good part is that the depression isn't simply a "bad attitude" of the sufferer. It is very real. There are several different types of treatment for major depression. Medications (there are many!) and various therapy types are the main treatments.
Different medications work for different people. It often takes a good amount of time to find the right medication to treat the problem. It also takes time for people to develop a sense of trust and honesty with therapists. That is the sad, hard part of the illness. Further, some people are wired with treatment-resistant major depression. It doesn't mean that people don't care about them, or that they don't care about other people in their lives. It's just very hard to enjoy life when the good neurotransmitter chemicals aren't attaching to the neurons in the brain.
That said, take a step back from your son if you need to. You do need to protect yourself and family from physical and emotional harm. But, do continue to show your eldest son that you do love him. Phone calls, regular visits, try to be there when he needs to talk so he can still feel that love you have for him. I wish you all the best.
Shez