New parakeet male or female? ?

I got a new parakeet named nero to add to the two i have, kai and cloud. Planning on taming it then getting it a friend. He has a seperate cage because the males would supposibly fight for the female. Well I introduced Nero to the other birds for a moment and cloud and nero, the males, get along FINE. Like theyve known eachother they're whole lives even though there's a nesting box in the cage. And nero and the female, kai, fight. So this is giving me doubt it is a male? Because females fight right? But its not major fighting. And males sing a lot more than females if females do at all and nero doesnt sing that much. His cere is CLEARLY blue. But even the petstore owner said the ceres can be wrong. She wasnt sure it was a male so she checked the feathers under neros tail to see if their were more ya know? But does this behavior normal for a new male? Do you think it is a male? Oh and clouds cere is a lighish purple but im for sure hes a male. And all of these birds are at least one year old