half-brother

half-brother — noun

1. A male relative linked to you by exactly one shared birth parent — your mother i

1.nounA2
Definition

A male relative linked to you by exactly one shared birth parent — your mother is also his mother and your fathers are different, or your father is also his father and your mothers are different.

Example

Apinya and her half-brother Ryo share the same father but have different mothers.

explains which parent is shared

Liam grew up with his mother, while his half-brother Kabir lived with their father abroad.

half-siblings raised apart

Common collocations
  • her half-brother
  • older half-brother
  • younger half-brother
  • half-brother from my father's side
  • long-lost half-brother
Synonyms
  • half-sibling

    gender-neutral term that includes both half-brothers and half-sisters; less common in everyday speech

Antonyms

Grammar Patterns

my/his/her half-brother

half-brother + from [parent's] side

Usage Note

Frequently used with a possessive (my, her, his) or a name. Unlike step-brother, half-brother always implies a biological link through one shared parent. If you need to specify which parent is shared, add from my father's side or from my mother's side.

Common Mistakes

My step-brother lives with us after my mother married his father, and we share the same mother.
My half-brother lives with us after my mother married his father, and we share the same mother.
step-brother means no shared blood parent; half-brother means you share one biological parent.
He is my half-brother from both parents.
He is my brother' or 'He is my full brother.
half-brother means only one parent is shared; if both parents are shared, use brother or full brother.

Word family

Synonym discussion

Sense: noun/1

Half-brother refers to a male sibling who shares exactly one biological parent with you — either the same mother or the same father. Step-brother is the most commonly confused term; it means the son of your stepparent from an earlier relationship, with no blood relation at all. Half-sibling is the inclusive, gender-neutral form that covers both half-brothers and half-sisters; it is more common in legal or formal contexts than in casual conversation. Full brother (or simply brother) means a male sibling who shares both parents. For example: 'Élise and her half-brother Ryo have the same father,' but 'Christopher is Élise's step-brother because her mother married his father.'

half-brother ↗step-brotherhalf-siblingfull brother

Common collocations

Nouns

Phrases

  • from my father's side
  • from my mother's side

Prepositions

Etymology

Old EnglishMiddle EnglishEnglish

The word half-brother was formed in Middle English by combining half (meaning 'one of two equal parts, partial') with brother ('male sibling'). The half- prefix signals that the biological relationship is incomplete — only one parent is shared instead of both. The earliest known uses appear in English documents from the 1300s.