Hello,... I saw your post about the sleepover, etc.
My guess would be that there may have been trauma in the family or to the other child, and sometimes there is a medical problem where a very slight operation at the tailbone area on certain tissue can relieve pressure that otherwise can lead to bedwetting -- it can make an amazing difference for those affected. Trauma can also cause bedwetting. The mother may have the boy sleep nude -- or it be his preference -- due to the nightly wet clothing. The problem could also cause him insecurity & trauma. I doubt she is nude herself when sleeping with him, and that seems a bit doting for an older boy.
He is likely used to being nude at night & didn't think anything of it, nor of being seen naked. Same with his mom.