Definition of "sibling"

sibling

/ˈsɪblɪŋ/

noun
plural siblings
1. A person who shares a parent; one's brother or sister who one shares a parent with.
2. (computing theory) A node in a data structure that shares its parent with another node.
3. (taxonomy) The most closely related species, or one of several most closely related species when none can be determined to be more closely related.
  Quotations
  D. simulans, D. mauritiana and D. sechellia (which we will call “the siblings” when we do not need to distinguish among them) have homosequential polytene chromosome banding patterns differing from those of D. melanogaster by one long inversion on chromosome arm 3R and a few much smaller inversions.
  1990 April 1, P. Hutter et al., “A genetic basis for the inviability of hybrids between sibling species of Drosophila”, in Genetics‎, volume 124, number 4, pages 909–920
  Bush suggested that this difference might represent a case of chromosomal polymorphism or, more likely, sibling species.
  2015 November 26, Lucie Vaníčková et al., “Current knowledge of the species complex Anastrepha fraterculus (Diptera, Tephritidae) in Brazil”, in ZooKeys, volume 540, pages 211–237