Ehhh.....there's no viable hard numbers on this.Turns out Brahmas need 9 hens to 1 rooster.
The 'rooster' to hen ratio of 1:10 that is often cited is primarily for fertility efficiency in commercial breeding facilities.
It doesn't mean that if a cockbird has 10 hens that he won't abuse or over mate them.
Many breeders keep pairs, trios, quads, etc ....short term and/or long term.
It all depends on the temperaments of the cock and hens and sometimes housing provided.
Backyard flocks can achieve good fertility with a larger ratio.