And some largefowl breeds do not have bantam counterparts
There are many, many breeds of chickens. Brahma is one of those breeds, and it comes in both largefowl and bantam.
Sex-links are a cross-breedwhere you can identify the gender of the chicks at hatching by their appearance. Black sex-links are made using the barring gene: breed a barred hen to a non-barred cock, and the barred offspring will all be male. Barring on a chick is indicated with a white head spot. Those with no spot will be female.
Red/gold sex-links use the silver/gold gene. Breed a silver hen to a gold/red male and the silver (white-looking) chicks will all be male, and the reddish/yellow chicks will all be female. This one you need to make sure that neither of the parents are white or carry white as that can make ID of chick gender impossible to tell.