I've often heard that Keens run a little big, this is my 3rd pair and have not found that to be true. Perfect fit on all

My son is 5yrs old and wears a kid's 13, do you know how that translates to Keen sizes? I see the sizes range from 1-6, are those the youth sizes or the kid's sizes? I know that my son would eventually move from a 13 kid's to a 1 youth, but I'm just not sure how these sizes run...any help you could offer would be a big help, Thanks!