Ok, heres a couple of possibilities he can run by his doctor...
1. Incorrect shoe for his foot-arch. When shopping for shoes, he should preferrably shop at either a sports - store or a green - cross store. They will be able to tell him what shoe shape will/will not work whereas normal shoe shops isn't always all that well educated on the topic. It is more important than what most people realise.
2. The shape of his foot-arch is abnormal causing problems with ... one, finding proper foot wear and two he might be turning his feet in/out as he walks/stands. As in my case, whereby I have a flat arch and turn my feet in, with the solution being to wear orthopedic inserts to support my "abnormal" foot structure as shoes are not made that can fit the shape of my feet.
I would suggest he sees a pediatrist to avoid possible further problems with joints such as his hips and knees.
I hope this helped...