the.com/sibling
your first rival, your built-in witness, the only person who remembers the crime with you
means a brother or sister — a person who shares one or both parents with you.
from From Old English 'sibling,' built from 'sibb' (kinship, relationship, peace among kin) plus the diminutive '-ling' — so literally 'a little relative.' That root 'sibb' is the same one buried in 'gossip,' which began as 'god-sibb,' a godparent, a person made kin to you by ritual. Curiously, 'sibling' nearly died out and survived only in dialects; it was revived by anthropologists in the early 20th century who wanted one tidy word for 'brother or sister' regardless of sex.
shared dnaFull siblings share about 50% of their genes
birth orderFirstborns score marginally higher on IQ tests
oldest bondSibling relationships often outlast both parents and spouses
deep historyVertebrates have had siblings for over 500 million years
twin trickIdentical twins share fingerprintsbut still differ slightly