You are trying to help someone who is ill and they accuse you of poisoning him? That is awful! Royce's suggestion of a letter from an attorney is a good idea. However, that can be expensive. Perhaps you should just remove yourself temporarily from the situation. Let the family take care of him while he's ill. You two can reunite when he's recovered. Before you leave do let your boyfriend know what the family said and why you are temporarily stopping to care for him.

I'm so sorry you are going through this. I hope things work out for you.
PML