My cats are indoor/outdoor which is the norm here in my country anything else is considered cruel here, but that is NOT my opinion, infact since being on PT I think if you can build a lovely protected outdoor area that is the ideal IMO, and what i dream about having one day,that way you can be assured of their safety and also see them enjoy the great outdoors, PURRFECT, so if you can convince your parents to build an outdoor area for the cats then that would be the best life can offer them, otherwise probably best to keep them indoors, if you can.