Kin Definition: A blood relative. Related Terms: Propinquity As in next of kin, referring to the closest blood relative.In re Smith's Estate, Justice Schwellenbach of the Supreme Court of Washington wrote of the common law as it existed in 1956."The meaning of the word kin is a blood relation."As between a stepchild and a stepparent there is no blood relationship, but only that designated as affinity, the relationship which one spouse, because of marriage, has to blood relatives of the other."Statutes have been impemented in most jurisdictions to erase the historical distinctions between blood relatives and those who are only related by bonds of marriage or adoption. REFERENCES:In re Smith's Estate, 299 P. 2d 550 (1956) Categories & Topics: Family Law Dictionary Trusts, Wills, Estates and Probate Law Dictionary Find you are constantly looking up definitions? Try our search provider (works in most modern browsers) If you find an error or omission in Duhaime's Legal Dictionary, or if you have legal term suggestion, we'd love to hear from you!