From Middle English half-brother, equivalent to half- + brother. Cognate with Dutch halfbroer (“halfbrother”), German Halbbruder (“halfbrother”), Danish halvbroder (“halfbrother”), Swedish halvbroder, halvbror (“halfbrother”), Icelandic hálfbróðir (“halfbrother”).
- 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.
- (a half-brother sharing the same mother): uterine brother; maternal half brother, maternal half-brother
- (a half-brother sharing the same father): paternal half-brother