Sororicide

Sororicide (from Latin soror "sister" + -cide, from caedere "to cut, to kill") is the act of killing one's own sister.

There are a number of examples of sororicide and fratricide (the killing of one's brother) in adolescents, even pre-adolescents, where sibling rivalry and resulting physical aggression can get out of hand and lead to the death of one of them, particularly if a firearm is available or if one is significantly older than the other and misjudges his/her own strength.

Compare with child murder (the killing of an unrelated child), infanticide (killing of an infant under the age of one year), filicide (the killing of a child by his or her parent), and patricide and matricide (the killing of a father or mother respectively by his or her child).

Known or suspected sororicides

 * Berenice IV of Egypt is believed to have poisoned her sister Cleopatra VI Tryphaena in 57 BC. She was later beheaded on the orders of her father, Ptolemy XII.
 * Cleopatra of Egypt requested the execution of her sister, Arsinoe IV, which was carried out under the orders of her lover Mark Antony in 41 BC.
 * Roman Emperor Caligula, according to historian Suetonius, killed his sister Drusilla after learning that she was pregnant with his child in 38 AD. Most historians now believe that she probably died of fever.
 * Roman Emperor Commodus ordered his older sister Lucilla to be put to death in 182 AD, after she was implicated in plots with members of the Senate to overthrow him.
 * Dipendra of Nepal (1971-2001) massacred much of his family at a royal dinner on June 1, 2001, including his father, mother, brother, and sister Princess Shruti.
 * Ronald DeFeo, Jr. shot his two sisters, Allison and Dawn, in 1974. Their murders became the inspiration for the Amityville Horror books and films.
 * Canadian serial killers Karla Homolka and Paul Bernardo raped, then accidentally murdered Karla's sister Tammy (1990).
 * Yuki Muto murdered his sister Azumi Muto on December 30, 2006 in Japan.