Potty training

how old are the average age for being potty broke?

Hi,
Adam has a very small break 5p15.3 to the end an is now 3 1/2 yrs. He will use potty if we sit him on it, but never asks, nor does he always seem to recognise that hes done anything. We just keep trying him on the potty every hour and hope that he will one day tell us. Good luck! Ann