I would agree with the spanking (as I was spanked as a child and I listened) however, a more important thing that I have learned lately is that spanking promotes hitting and so it may help solve your problem now, but you may have much bigger problems if he starts hitting children in school, his brother and sisters, etc. and there are other ways to help solve it that are likely to be more effective without a negitive effect. Have you made sure that he is not affraid to get up and go to the bathroom by him self in the middle of the night? I would make sure the path to the bathroom is well lit and the bathroom as well.