Night time potty train FAIL

My son is 4, day and nap potty trained. Nighttime he still wets the bed. He was wearing pull ups but on Nov 1, I switched him and his 2 year old brother to just undies. We said bye to pull ups! Well his brother succeeded, zero accidents. But i knew he would because he was waking up dry or walking me up to potty (neither one of them will get up by themselves and just go, the 2 year old will wake me up to take him) the 4 year old just isn't getting it. Since Nov 1st, he's woke up dry twice. But most nights he wets the bed 1 or 2 times. Sometimes he sleeps right through it and doesn't even notice. Most times he wakes up crying until I come in and change him then falls right back asleep. I am starting to think he wasn't ready but now what?!I can't revert BACK to pull ups right? He wasn't even using them like pull ups, he was using them like diapers. He has no problem with a wet soggy diaper. He's really intelligent, very active, funny, sensitive but stubborn. He has no developmental issues. So now I don't know what to do. Keep trying? Or go back to pull ups? HELP!