"This is the man whose brother is my friend."
Translation:Αυτός είναι ο άντρας του οποίου ο αδερφός είναι ο φίλος μου.
It seems that man (male) is considered the only human being on earth :) At least Greek make a discrimination in genres, that means that Greek is more feminist than English. Joking :)
About the word "ανθρωπος" and its origin there are many theories about its etymology. It is actually unknown, even the most common one is that it is from the Ancient "άνω"=up and the Ancient verb+ "θρώσκω"=jump +όπωπα (Ancient past participle of the verb "ορώ"=see), that means a person who looks up, has dreams and scopes in life, a version that it was very famous when I was a student. I don't believe it anymore, it it just a romantic and too exaggerating etymology. Most likely the origin comes from "ανδρας" (ανήρ in Ancient Greek) and "όπωπα", that means a being that looks like a man (male). So it is as in all the same origin languages: άνθρωπος=man, male and γυναίκα=woman. So no feminism at all! But for sure it is a very ancient word: https://el.wikipedia.org/wiki/%CE%86%CE%BD%CE%B8%CF%81%CF%89%CF%80%CE%BF%CF%82#.CE.95.CF.84.CF.85.CE.BC.CE.BF.CE.BB.CE.BF.CE.B3.CE.AF.CE.B1
It does not need it, but it is correct. It is needed when you were talking about this friend of yours and want to emphasize that you refer to that friend once again. Otherwise just saying that "he is my friend" you say "είναι φίλος μου". In multiple choice, you have to select all correct answers, and both are correct translations. ;)