My mother had 6 siblings and 5 of them wet the bed until mid teen years. Then came my generation with my cousins. 65% of us wet the bed into our teens as well (80% of the males). Many things were tried, alarms, medications, etc., but nothing seemed to stop it. We simply all grew out of it. One of my uncles was appointed to Navy academy and the family was ultra-worried he'd have to call it off due to his bed wetting. Luckily, it stopped just before he graduated from high school.
I was an extreme deep sleeper and I believe a lot of times that has something to do with it. I'd be like in a coma when I fell asleep. I swear they could have dressed me in a clown suit while I was sleeping and I'd never wake up. It appeared (although no testing was done) that it was totally genetic in nature. I feared to have kids, but I had 7 and not one of them were bedwetters. My wife still counts it strange that while courting I asked her if she had any bedwetters in her family. Whatever, her genes seem to cancel out that issue. Interesting too that then the next generation we (our extended family on my mother's side) were down to only about 25% being bedwetters until teen years. None of my 20 grandchildren have had bedwetting problems outside of toddler years.
It was devastating growing up with the problem because it made it so I couldn't do sleepovers and such and had to worry when kids came over to play with the smell that lingered in our bedroom. Boy Scouting was tough, but one of my 2 brothers was like me (he was a year older), so we worked together to make sure other kids didn't find out. We made sure we were in tents together. This was before they had pull-ups, goodnights, etc.
My one grandmother (the one that didn't have all the kids that were bedwetters) would get my two brothers and me up at night if we stayed with her to go to the bathroom. That worked, most of the time.
In the aftermath years later, my biggest complaint was that my mother never told me that she herself and 4 of her siblings wet the bed until their teenage years. That info would have been helpful--very helpful. It would have been great to not feel that I wasn't some freak. I didn't know until I was well into my adult years. She was just that embarrassed about it.
We had a younger brother of some of our kids ward friends who I had found out was a bed wetter. I didn't know and he had "tagged" along with his older sibs and we let him stay the night. We had younger boys just under his age that liked to play with him. The first time he spent the night I found the next morning that he had wet the bed that night. I confronted him about it and he told me that he just sweat so much at night.
When I told him that I was in the same boat as he was at his age, he got such a huge smile on his face, because he was 9 years old at the time and felt he was a freak too. From then on he wanted to come over almost every weekend if we had let him. When he did stay, I'd get him up at night, just like my grandmother had, and march him to the bathroom. That worked about 90% of the time. He didn't want anything to do with "disposable absorbent underwear" for nighttime. He had a younger brother (1-year younger) that was also in the same boat and he started to come over as well with his siblings knowing we were a "safe haven" for them with their problem, but he had no problem wearing those items and would make sure he had it on before he went to bed. I wanted so much for them to understand they were okay and not defective, as I had felt growing up. I sat my children down and told them of my story and asked them to please be conscious of those boy's problem. They were stellar and never made fun of them or shared that info with anyone. I was so proud of them. Both of those two boys, just like I had did, eventually grew out of it. They stopped at about 12, my brother and I were about 15-16.
Just help him understand that it's not anything that's wrong with him and on some time schedule those wet days will end.