Tiffany; there is nothing to apologise about. It had to be a very emotional and upsetting experience. It is hard to see people suffer. It is hard to experience peoples inability to be able to rise to the occasion and give sick people some love, support, and understanding. He is lucky that you were there for him in what must have been both a scarey and disheartening experience. It's sad, but many of us just don't know how to respond in emergencies like this. It sounds as if what he experienced, and what you witnessed was fear, anger, shame, and perhaps a strong desire to not confront the reality of what was happening.
I do not have HIV. I am just "on loan" from the sister Hepatitis C board.

So I am not really an experienced HIV/ AIDS guy. I do have some experince in having a disease that has negative stigma. Many of us HCV infected end up keeping it secret also so that we can be treated normally...... or we can be employed...... or NOT judged....... or so our children are not punished for our disease. I can tell you that meeting a kind soul like yourself is a real blessing. Your father in law is very forunate to have someone in his family that is compassionate.
So far as what should you do......... My sense is that there is no one "right" thing that will work for all families. In this case, you have the right to treat him as you desire. Perhaps his other family just does not know how to properly respond. I also believe that people have the "right" to respond in their own time. Some people may not be able to "deal" and so withdrawl. We ultimately are responsible only for our own actions.
I hope the doctors can help him pull through. Now that this is more out in the open the issues can start to be worked on.
Thanks for writing, and take care.
Best,
Willy