My son is 7 now and wears GOODNITES® Underpants every night. In his case, it is hereditary. His father and his father's brother and their father were all bedwetters. The reason for that is because they are all very heavy sleepers. The feeling of having to go to the bathroom did not wake them up. My husband said that he and his brother were taken to a doctor that gave them a mat that was hooked up to an alarm, and every time the mat got wet the alarm would go off and wake them up. After a period of time using this method the problem eased up.
My mother said that I never once had an accident in bed. So the problem certainly comes from his father's side. My son does sleep sound just like his father. I do wake him up and take him to the bathroom before I go to bed. This causes no problems with him because he gets back in bed and goes right back to sleep like he never got up. I do make sure he does not drink after a certain time, and this does seem to help a bit.