An Etymological Dictionary of Astronomy and Astrophysics

A person’s brother or sister.

Etymology (EN): M.E., from O.E. sibling “relative, kinsman,” from sibb “kinship, relationship; love, friendship,” cf. O.Saxon sibba, M.Du. sibbe, O.H.G. sippa, Ger. Sippe “kin, related,” Icelandic sifi “related.”

Etymology (PE): Barxâ, from bar- first syllable of barâdar, → brother, + xâ-, short for xâhar (x^wâhar), → sister.
Hamšir, literally “of the same milk,” more specifically “sucking the same breast.” However, a hamšir may not be a person’s brother or sister.