We don't have synonyms for half-brothers yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are half-brother, half brothers and half brother.
(n) :
Alternative spelling of half brother. [A male sibling sharing a single parent, as distinguished from a full brother or brother-german, from a step-brother, or from a brother-like figure such as a blood brother.]
(n) :
Alternative spelling of half brother. [A male sibling sharing a single parent, as distinguished from a full brother or brother-german, from a step-brother, or from a brother-like figure such as a blood brother.]