I would try to find out more about the issues and see if there are any support groups or counselling services that can help you and the family to cope. Talking to others who have to live with similar problems can help, are there any on line forums for those in your situation?
You have my sympathy, people often overlook how hard it can be to, in effect, ‘lose’ a family member with all the usual expectations of love and friendship, sharing life goals and so on, etc that go with having a ‘normal’ spouse, child, or grandchild. However, in reality, many family members end up lost to drugs, drink, crime, serious illness, life changing accidents etc, and depression among the young is becoming increasingly common. We have to let go of all our preconceived expectations and find and love all the positives that are still there. So sad for the person themselves, but also very hard for their family.
May you find the strength to give all the support they will need. ?