Fratricide

Killing your sibling. Also used for killing your brother-in-arms, your fellow soldier. From the Latin fratricida. Frater (brother) also appears in fraternity and fraternize. Cida (killer) appears in all sorts of words.

• Suicide - killing self
• Homicide - killing another person
  
• Genocide - killing a cultural group
• Regicide - killing your king
• Insecticide - killing bugs
  
• Deicide - killing God
• Vaccicide - killing cows
• hirudicide - killing leeches

and my favorite...

• Onmicide - Destroying everything

You can -cide just about anything you want using Latin and English. Art is Cain practicing fratricide on Abel from a 12th century mosaic.