My boy last year was in a similar situation a young boy with a bunch of older girls. Even once he came of age three was a distinct line between him and the head girls. At first he had no good to walk on and would be run off or attacked by one of the head 3 for even attempting to mount a hen. But he was a good boy and never bothered the younger pullets as they weren't laying yet. Slowly he learned and worked his way up the ranks as any hen would do in the pecking order. It quit well took months for him to earn his role. Over thing I did learn from watching him is young roosters don't always tend, or treat their girls, they just want the booty call. As he grew he learned to treat them with respect. Now he is a little over a year, he finds bugs and will call for or take it to his girls, and he dances for them. He knows who he can mount and who he has to court. It's funny to watch him dance for some of the oldest girls only for them to turn and walk away, he'll sulk for a minute or two and go about his business. But I know he does get his bits with them once in a while becuase I have fertile eggs from all my girl.
Give him time they will all learn
