New shoes

I noticed yesterday that Jacob's shoes were quite worn at the toes. So I hit up some Black Friday sales to find both boys some new shoes. Isaac was barely squeezing into his (that he's worn over a year and were Jacob's). I was sure Isaac's were a size 4 and Aaron told me Jacob's were size 10. So I figure size 5 and size 11 would be perfect. I can't find any 11s so I went with a 12 hoping it wouldn't be too big. I get back and have the boys try them on. Aaron put Jacob's on and I did Isaac's. I notice his aren't much bigger. Come to find out, his old shoes were a 5! Great. I check out Jacob's and his toe is at the very end!! How on earth could he have been wearing 2 sizes smaller this whole time?! Maybe this is why...