At ds's birthday party last month (dh's) BIL refused to use the downstairs guest bathroom & kept going upstairs to use the main bathroom - found this odd but fair enough , everyone else was happy to stay downstairs & use the bathroom . Later that night when everyone had gone home i noticed the attic door was fully open 
now this door is high up in the ceiling with no stair access so difficult to open (you would need to stand on the stair banister to get up there or get a ladder and the spare bedroom door was also open (junk room always locked )
We said nothing to Bil but now its DD's birthday party on Thursday & BIl will be here again & i am sooo tempted to bring it up in a jokey kind of manner ( something like "oh we must have some v strong mice in the attic as they are able to open the doors") but dh doesn't want me to .
What do you think ?