Sororicide

Sororicide is the act of killing one's own sister. The term is Latin in origin, stemming from a combination of the Latin words Soror (Sister) and Cide (To Cut/To Kill). There are as many 7-9 cases of Sororicide dating as far back as 57 BC.

On Criminal Minds
Sororicidal killers featured on Criminal Minds
 * Season Eight
 * Sera Morrison ("All That Remains")
 * Season Ten
 * Benton Farland ("Amelia Porter")
 * Jerry Tidwell ("Beyond Borders")
 * Marc Clifford ("A Place at the Table")

Real-World
Real-world Sororicidal killers
 * Paul Bernardo and Karla Homolka