My ex mother-in-law used to take care of her husband (he has since passed away) this way. She would wait on him hand and foot. If he was home, the tv was on the station of his choice. She went where he went and took an interest in his interests (took up golf) because that's how she could spend the time with him. I could look at their relationship, not like it, and know that's not the kind of relationship I wanted.... but she was happy. She loved her husband and chose to dote on him this way. I can acknowledge it without getting angry or upset about it.

I would try to let it go as it could ruin your relationship with this family, with your boyfriend. You don't have to like everything about his family, but you don't want to be a cause of friction.

Also, did you say they are both 70? At 70, I would not assume he is faking anything.