His bedwetting isn't uncommon. I started bedwetting at around 14-15, and like your son, my bladder wasn't growing as fast as I was. I had to result to diapers, because it just wouldn't stop. I would start by not letting him wear his diapers around the house. I dout he has a fetish now, its probably more of a "convinence" issue. Hes got it on, why worry about getting up and going to the bathroom? I know the feeling, and trust me, most times I would much rather just wet my diaper than actually get up, take it off, and go to the bathroom. Of course I don't, but none the less, the feelings there. So prevent the feeling. Have him put the diaper on right before he goes to bed. The fact that he goes around in just a diaper and tshirt shows he is completely comfortable with his diapers, so a fetish may be possible. Personally, I wouldn't be got dead in front of my parents in a diaper and a tshirt. I do sleep in just a diaper and tshirt, but I put on some boxer shorts to walk around the house in. But we are all different, and are all on different levels. It might be just a sign that he is comfortable with him self, and his relationship with his parents. Your son is normal. Its obvious you all have a good a relationship, so don't do anything that will harm your relationships. Make the changes gradually. Don't shock him one night, telling him to not put his diaper on untill bedtime, go into it gradually, sit him down and talk to him about your concerns. Maybe it will help him open up, and talk to you about what he is feeling. It may be a tough discussion, but its one you have to have. Maybe have his father do the talk, if hes more comfortable with him. But remember, a fetish to diapers is not the end of the world. It may come is a shock. Personally, I would much rather have my son like diapers, than be going out and doing drugs, drinking, having sex. If he does like diapers, then don't forbid him from wearing them. He will just revolt. So he likes diapers, in this day and age, things could be much worse.