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