I'm sorry I don't have any words of wisdom, but just wanted you to know I am thinking of you and your family member. It is clear by your post that you really care about them and want to help them. Would it be possible to inform their GP of their wish to stop their medication? If your family member won't see their GP, could you go along to speak to them? This of course would depend upon the GP speaking to you about them, but it is maybe worth letting them know what is going on anyway to see if they can do anything.
Apologies that I can't be of more help to you, but can appreciate how difficult this must be and hope things work out for the best. Aileen x