1. The problem statement, all variables and given/known data Is this relation symmetric? The relation in a set of people, "is brother of" 2. Relevant equations aRb , bRa 3. The attempt at a solution The answer is not symmetric. They gave example says that paul may be the bother of Anne but Anne is not the brother of paul I thought that if A is brother of B then automatically B is brother of A isnt it? I think the reason why i can not understand this is problem of English. In my country brother indicates both older and younger, is it different in other country?