My mother lives with me and has no idea that I am her youngest child. Some days I even show her my birth certificate and it means nothing to her.
She will still ask me questions like "So...how long have you been her". That lets me know that I can not get through to her. I think you will not be able to comfort your family members any more than reminding them that you are there everyday and he really does not know you. You are only a safety net of familiarity. The same as the people that live together in assisted living...they don't know each other, but they know that they see each other everyday. My mother has been away from independent living for almost 4 years but will even still fuss and fight if you try to tell her that she does not still live alone. The burden is on the loved ones that are of sound mind to keep a healthy mental balance about the illness. You can't fix this situation...that is what I have had to learn and accept about this illness.