Do you still have keys for your parents' house? Or if they moved out of your 'childhood' home after you left, did they give you a set?
Do you use them? Do you drop in unexpectedly?
I still have keys to my parents', I do use them if I'm visiting, but almost never pop in unexpectedly. I have on a couple of rare occasions gone in unexpectedly when I knew no-one would be in.
My dad has keys to his parents' house but never uses them, even if he's been invited and they know he's coming, he will knock and wait for them to answer the door to him.
Do your parents have keys to your place? Mine don't, and the ILs don't either. I would feel a bit funny about it TBH, which is highly hypocritical! I might give my grandparents a set though, for emergencies, as they will be the closest family.