The trick I always use and has never failed me yet open the diaper up a little bit peak inside and if his his penis starts to go up put diaper back down and wait a few min a then check again u should be good. When fresh air hits down there makes them pee a good bit of times same with girls
lol sometimes they stop, my boys haven't peed on me in a few months knock on wood lol except now that I said it they're gonna start peeing on me again lol