Advice about my lazy grandaughters husband?

my grandaughter is 22 and married to a very lazy man of 30 they have a 5yr old son she has a part time job he sits at home all day playing ps2 games the house and the garden are a tip it upsets me very much to see her living like this shes accepted this way of living but i know it does upset her i dont know how i can get him of his bum and get him to do something to improve there home ive talked to him he agrees at the time but then he forgets it all and continues sitting on his backside. we even bought the things for them to decorate there lounge but he put them in a cupboard and there they stayed. there son cant even play in the garden as its in a mess he wont even clear that up for his own son. can any one tell me what to do i dont want to have a go at him as that will upset my grandaughter and were very close.