Did you take your cat to live with your parents? How old is he? Are there other cats or animals at your parents' house?
He sounds like he might be very stressed. Some cats get stressed much more easily than others, and one way that cats show this is to poop or pee outside the litter box.
But your cat may also be sick, and should be taken to the vet for a checkup when there is a sudden change in behavior like this.