How to deal with the loss of a family member who chose to die?

Seek Therapy! Dealing with death of a loved one is very difficult; dealing with suicide is even more complicated, because each individual reacts emotionally in their own way. There are no "typical" answers, because each person has to find their own individual way to deal with such loss. In my opinion, see a very good therapist (psychologist, social worker or counselor), experienced with loss.