Cuz Remus and Romulus as per legend were the founders of the city of Rome... They were twins who were abandoned and found by a She Wolf who took care of them and suckled them with their own milk... Jo's character names have a lot of meaning... going by that Lupin should have a twin Romulus who will turn out to be R.A.B... It will later turn out that Lupin is only an assumed surname so that his family is not affected by his werewolf tendencies... His surname is actually something with B ... Or Lupin's twin has an assumed surname with B ... What say??
R.A.B being Regulus Black will be too obvious..!!!