5 weeks ...I see why he invited you. And I didn't automatically think you displaced her from a particular bed. I actually thought it was possible that her health condition made that her preference be it home or on vacation.
Sounds to me like some event trigger the ending of intimacy and the opening of their marriage. She fell in love with another guy, he cheated on her with her sister...he got drunk and hit her ....something..<<(wild examples ) But worth a look.
Lets say then her feeling shifted towards roommate, business partner but because she/they don't want to trash the family or lose the house and life they come up with this plan. He's free to seek out other women because she didn't care ....she doesn't see him that way anymore. Then she got sick ...and then he was the one taking care of her. If this wild speculation was even partly true the complex set of emotions she'd have ...love, admiration, guilt, shame, etc. etc. The illness has jammed everything up on both sides.
Is there a dominate partner in their relationship....Who calls the shots? Or who did before the illness if that applies ?