I have a four month old dark brahma that was supposed to be a hen, but I've suspected he was a cockerel for some time. But I want to be certain before I have to let him or one of the other roosters go, please help.
That looks like a boy. Brahmas age slowly so it can take some time to be sure, but by now I am seeing a black breast, white back and large pea comb= boy. Girls look more grey from a distance and if you zoom in on the feathers they will be a steel grey with very distinct pencilings (lines or bands or rings of black around and inside the feather base color) and are rather uniformly colored except for the hackle/neck which appear more of a white and black penciled.
I have never had a Brahma roo, but the ladies are super friendly and very sweet!