What is fratracide?

You probably mean Fratricide.

Fratricide (from the Latin Words frater "brother" and cida "killer," or cidum "a killing," both from caedere "to kill, to cut down") is the act of a person killing his or her brother. Related concepts are sororicide (the killing of one's sister), child murder (the killing of an unrelated child), infanticide (the killing of a child under the age of one year), filicide (the killing of one's child), patricide (the killing of one's father), matricide (the killing of one's mother), mariticide (the killing of one's husband) and uxoricide (the killing of one's wife).