Hi zorna, Welcome to healing well forum. I am sorry about you and your brothers loss. Did she pass away or is it from divorce? Either way can be devastating for the person. Alcohol works as a depressant in the body, when someone turns to drinking or increases their drinking due to an event such as this they usually do it as a means to escape or an attempt to feel better or numb the pain. But the alcohol works backwards towards this and ends up making the person more depressed.
I understand it is difficult to watch someone you love go through this and torchering themselves in this way. My suggestion would be to keep on him about counseling, and perhaps read up on alcohol and depression related articles that are available..there are many on the Internet that are quite good. You can print them out and take them to him, and perhaps his child can even try to put some pressure on him getting help. I am sure that at 16 yr of age they are more than aware of what is going on and it is effecting them in some way shape or form.
I wish you and your family much luck..perhaps another member will also have some suggestions for you on this, I am sure. Please do post again and let us know how it goes. Take care