It's not unusual for everyone. If they went to bed for the evening maybe they simply don't wear pajamas. I sleep in the nude all year around (and yes, that means no undies, or you wouldn't be defined as naked), even when it's below zero out. I know. TMI. LOL
Hot weather? I use less blankets or kick them off entirely. Cold weather? More blankets, but NEVER pajamas, so I don't find that odd or unusual at all if they had retired for the evening.
So if they had retired for the evening, and found dead in their beds, then what killed them both at the same time? So for me, I'm not suspecting suicide. I'd never consider dying by suicide, but if I did, I certainly wouldn't undress for the act KNOWING someone was going to eventually find my body. And I'd likely not get under the covers if I was waiting for something like a poison to do its work. I'd sit in an easy chair, the couch, or lay on the bed, not under the covers. MOO
ETA - When I'm talking about "for the evening" I simply mean
when they go to bed to sleep as it's been reported they were up at night and slept in the day.