The term ROMULUS' TWIN refers to the twin brother of Romulus, the legendary founder of Rome. His name was Remus, a five-letter word which is the solution to the crossword. According to Roman mythology, Romulus and Remus were the sons of Mars, the god of war, and Rhea Silvia, the daughter of Numitor, the former king of Alba Longa. They were abandoned in the Tiber River and were rescued by a she-wolf who nursed them until they were found by a shepherd. The twins later fought over who would rule the city they had founded, and Romulus killed Remus.