A.R.
I had this same problem with my youngest. After too much yelling and hair pulling (and a trip to the U of M for diabetes testing) I finally took her to a naturepathic physician who gave me the answer: blood sugar.
Blood sugar levels drop and send a message to the brain to release the bladder. This is why they can't tell you WHY they are peeing in their pants. The message is going to the bladder sphincter automatically and without their knowledge.
The trick is to keep their blood sugar levels up throughout the day.
Make sure they are eating a lot of protein, fruits and vegetables. Protein can include meat, beans, eggs and nuts - but make sure any nut butters you serve them are unsweetened.
Avoid sugar as a regular food source and limit the filler foods (bread, pasta, rice and cereal) to less than 1/2 the amount of food you are giving them at any one time.
I give my daughter a breakfast with sausage, bacon or eggs every morning and add toast once she has eaten plenty of protein. This typically starts the day right on the blood sugar issue and most of what she eats later will be well-balanced.
I also don't feed her sweets much - perhaps 1x a day or less - offering her fruit instead. The sweets I have around the house are corn-syrup free and are pretty low calorie.
I hope this helps B.. My daughter's problem cleared up OVERNIGHT with this attention to her diet. Even her bedwetting stopped.
Don't blame the boys. It's most likely their blood sugar. Also, regulating it at this stage will help to avoid late-onset diabetes later on.