A murderer or perhaps a Kinslayer.
The term you are probably looking for is "fratricide"
Fratricide is the killing of one's brother. Sororicide is the killing of one's sister.
Regicide
a murderer.
She will be referred to as the sister of someone's brother-in-law.
carer
Your brother or sister.
a butcher
If person married to your brother is a woman? She is your Sister-in-Law.
Your brother's wife would think of you as her brother-in-law and when wanting to get your attention will simply call you by your first name. If she is introducing you to someone she would say, 'This is my brother-in-law ____.'
Brother Joe might be someone who is a fellow christian in a church or it could be Brother Joe from the Elks Lodge or the Masons or other organizations where they recognize each other as "brother" because of their closeness.
Fratricide is the killing of ones brother or sister So you would call him a( Murderer )
civil war, brother kills brother.
Civil War. Brother kills brother.