A family member owns a holiday let and invited us to come to stay. They were staying at the time too, as they often do when they dont have bookings. They gave us their bedroom and slept in a different room so that DH and I could share the double bed.
One particular night, we had quite a few drinks. Once we went to bed, DH and I had sex. I know we were extremely quiet as we always are due to DC sleeping in bedrooms next door at home. Also, the other bedroom that my relative was in was far enough away to be certain they wouldn't have heard anything, but I woke up in the morning and felt awful about it as we really shouldn't have done that in their bed. We were staying with them for a week so we should have just held off. It was DH who instigated it and I think alcohol was definitely a factor.
This was a couple of months back and I still feel pretty awful about it.
I'm building it up in my head to be something terrible and am dreading seeing said family member in future.
YABU - you really shouldnt have done that
YANBU - its not that big a deal