I wet the bed until I was 9, my brother until he was almost 12, but our older sis never did. In our case, we were such deep sleepers that we simply didn't wake up. My mom started waking us every night about midnight and made us go to the bathroom. To this day, I still wake up in the middle of the night to use the restroom. My mom never had this problem and neither did the sperm donor as far as we know. I think each kid has different reasons why they do this.