Mmm sounds early but then again my mum never fails to tell me how I was tt'd by the time I was 18 mths old so it can't hurt to start leaving a potty around and showing him what to do. I did the same thing for mine at the same age although they both trained at around 2.5yrs. Anyhoo - could you try overalls so he can't get into the nappy or else I was going to suggest a body suit as well. Good luck!