Well, when you consider that all Thais hit a brick wall mentally at the age of about 12, it's quite understandable.
My 10 year old spent the first 9 years with his grandparents, sleeping in the same room as them and is backward ans still pisses the bed.
Our 3 year old has always slept in his own room and takes himself to the toilet when necessary. He far surpasses the older lad in most other ways too.
Oh, and any parent that sleeps with their kid past 1 year old should be shot.