It may be therapeutic to you to help others if you cannot help your family member. Recognizing that a person has limited capabilities should not mean that you expect nothing of them. Don't be afraid to ask your family member if he is thinking about hurting himself. Your own relative could be one. Discuss it to avoid it.
Mental disorders affect more than the afflicted.
Your conflicted relationship may spill over into your relationships with others. You may unconsciously reenact the conflicted relationship. It is natural to experience a cauldron of emotions such as grief, guilt, fear, anger, sadness, hurt, confusion, etc. You, not the ill member, are responsible for your own feelings. Allow family members to maintain denial of the illness if they need it.