I just learned they went on a trip
Change the locks.
Actually they screwed up my locks as well, while they lived with us they kept using the wrong key and tries to force it into my locks (this should give you the idea of the IQs). Had to buy new knobs at my own expense.
Also they always turn down my AC at their own leisure whenever they go into my house.
Of course, they also leave the door unclosed when they left at times. The only time they care to close it is if they left the kids behind.
The other thing they do is not training their kids to put things in the trash properly, so there are candy wrappers I had to pick up everyday coming home from work.
It's not the first time I talked to them about some of these things. Talking to them is like talking to monkeys, well.. monkeys are more intelligent than they are with better manners.