A sibling may be the keeper of one's identity, the only person with the keys to one's unfettered, more fundamental self.
A sibling represents a person's past, present, and future.
Siblings: the only enemy you can't live without.
Your siblings are the only people in the world who know what it's like to have been brought up the way you were.
Siblings: your only enemy you can't live without.
Siblings are the only people who will pick on you for their own entertainment and beat up anyone else who tries to do the same.
Siblings are the people we practice on, the people who teach us about fairness and cooperation and kindness and caring, quite often the hard way.
Siblings: the one who gets in trouble with you, but also the one who takes the blame for you.
Siblings: children of the same parents, each of whom is perfectly normal until they get together.
Brothers and sisters are as close as hands and feet.
Siblings: the people who know you the longest and still somehow love you the most.
Siblings: the ones who can drive you crazy one moment but make you laugh uncontrollably the next.
Sibling rivalry: a little healthy competition between brothers and sisters that makes us stronger together.