Have you tried putting your cats paws in his litter box and just let him stand there a while in there with the littler on his paws? If not, try that and it might work that he goes to the litter box. That's how they come to believe that they own the litter. Also keep the box in the same spot all the time. Cats get anxeity when the litter box is moved...If you are moving the box, you might have to retrain them for them to get used to the transition. I hope that this helps.
As far as cats being toilet trained, I haven't done it myself, but I know someone who did. They do have to be comfortible with the litter for you to toilet train them.
