sibling

A person who shares a parent; one's brother or sister who one shares a parent with.

None of my siblings are married yet.

A node in a data structure that shares its parent with another node.

The most closely related species, or one of several most closely related species when none can be determined to be more closely related.

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.

Bush suggested that this difference might represent a case of chromosomal polymorphism or, more likely, sibling species.