Maybe if you posted pictures, we could figure something out. Splay leg or slipped tendon, these can be fixed with little splints for "physical therapy."
If they won't eat, though...Some of my new chicks have gone the first few days without eating, no problem. You can try "pecking" at food with a finger to try to teach them. But if they just won't learn, even after a few days and you trying to teach them, brownchickenfarm is probably right; it would be mean to let them suffer. Baby birds can survive a lot, but not without eating.
you can make braces for him . tape his feet on thin cardboard cut to the shape of his feet. then take a bandaid, and cut it half the long way. wrap the piece around each ankle and leave most of the white separating the legs. he'll get used to it. then make a small bowl with feed and water , take him out and make him stand at it. keep putting him back. put a glob on the top/side of his beak. do this every few hours until he is digging in. also offer water. in no time he'll be running around attacking his feed.