No, the term 'soul brothers' is a compound common noun, a Word for anyone calling themselves soul brothers.
A proper noun is the name of a specific person, place, thing, or a title; for example:
- Soul Brothers Five, a singing group of the five Armstrong brothers until John Elliston joined the group and they became Soul Brothers Six.
- Soul Brothers, South African urban music group, recording artists
- Soul Brother Records, London, UK
- Soul Brothers Barber Shop, Jamaica, NY
- "Soul Brothers" album recorded by ray Charles and Milt Jackson 1958
