fratricide: a person who murders their brother or sister
murderer: a criminal who commits homicide (who performs the unlawful premeditated killing of another human being)
scallop: one of a series of rounded projections (or the notches between them) formed by curves along an edge (as the edge of a leaf or piece of cloth or the margin of a shell or a shriveled red blood cell observed in a hypertonic solution etc.)