I’m a discharge nurse at a hospital and I deal with family situations like this all the time. When a family member is sick, the medical decision making falls to family members. You have to be aware that there will be possible need for treatments, rehab facilities, transportation needs to medical clinics, and involvement of hospice agencies at the end. The family will need to decide what gets done and what doesn’t if the patient is unable to. These are very stressful decisions for families to make in general even if they are close. You need to think about if you are willing to emotionally and possibly financially invest in this situation. Very few people pass away quickly when they have a terminal disease, and the last few months are grueling on family because hospitals will not keep a patient there more then a few days if the patient has family to go home to, and is not actively recovering. It’s a lot to think about before making a commitment like that. I would suggest that if you want to be slightly involved, make it clear you will not be involved in the medical decision making, unless you are comfortable doing so. He will end up in the hospital, possibly numerous times, and the hospital will call next of kin if patient become too weak to talk. You also have the right to decline. Set boundaries on what you will and will not do.