person of different bloodline; non-relative
Refers to someone not related by blood, often in contexts of family, lineage, or clan. Can carry a nuance of outsider status.
He is not a blood relative, but he is treated like family.
different race; different tribe
Used for ethnic or tribal otherness; can appear in historical, anthropological, or fantasy contexts. May sound old-fashioned or formal in everyday speech.
The legend tells of battles with a different tribe.
Compound of 異 (i, 'different') and 族 (zoku, 'tribe, family, clan'). The exact historical derivation is uncertain, but the kanji straightforwardly indicate 'different clan/race'.