When I was 18yo, my boyfriend told me I walked on the inside of my feet. I hadn't noticed - and didn't really see it then. My shoes didn't wear unevenly on the inside. Fast forward 20yrs, my husband told me the same thing. Again, I didn't see it. My feet/ankles didn't hurt; shoes didn't wear unusually.
Forward again, 8yrs later - I definitely notice now, at age 46. My ankles hurt most nights. There is an odd bulge on the outside of my right ankle. I don't even know where to begin to correct this issue, but I'm afraid if I don't, my elderly years will be spent sitting because walking will be painful.
I'd advise having your son's feet checked out by a professional now to avoid problems in the future.