Sibling
WordNet
noun
(1) A person's brother or sister
WiktionaryText
Etymology
sibling. The term apparently meant merely kin or relative until the 20th century when its necessity for the study of genetics lead to its broader use. For example, the OED has a 1903 citation in which "sibling" must be defined for those who don't know the intended meaning.
- "1903 K. PEARSON in Biometrika II. 369 These [calculations] will enable us..to predict the probable character in any individual from a knowledge of one or more parents or brethren (‘siblings’, = brothers or sisters)." ("Sibling," OED.)
Noun
- A person who shares same parents. One's brother or sister.