I have one Rooster, Brahma if that detail is needed.  Hens vary 1-3 years, and there are some pullets. It might be due to the fact the cockerel is a cockerel. Also, he is very desperate to mate. Which makes him end up trying to chase them in his deep desperation for a mate. The fact that he is young, most of the hens are older than him, and that there is another rooster may be why he isn't liked. He's still trying to be a rooster, as evidenced when he's had some corn in front of him, and he started quietly calling the hens, to no avail. It might not completely be age, as there is the other rooster others have gotten used to, and the second oldest ones are fine with him, and he's younger. However, he bears a resemblance to the other Brahma rooster that needed to be removed due to aggression towards us who was older. I think our cockerel just kind of makes our hens and pullets uneasy due to this, but I don't really wanna gut him since he's still trying to be a proper rooster, he's just denied mating from the other one. I also do not have a separate area for him. Judging by the age pullets start to lay eggs, 16-24 weeks would be a fair estimate. 
I'm just wondering now if I should give him away. He seems to be trying to be an exemplary rooster, but I don't think he gets the chance in my flock... Although the pullets do roost with him.