What was romulus and Remus famous for?

They are the twins who founded the city of Rome according to the myth.

-- There's so much more, though. They were supposedly the children of a Vestal virgin who was seduced by Mars. The children were left exposed in the wilderness and suckled by a she-wolf until they were later found and raised by people.

They are also important because their mother was connected to the royal line of Alba Longa, which traces it's roots to Aeneas, the son of Anchises and Venus. So they claimed divinity from two sources, and claimed rulership by divine right. It is also important to note that Julius Caesar could trace his family heritage back to Romulus.

It was only Romulus who founded Rome. The twins had a dispute about where to found Rome, with Romulus wanting it on the Palatine Hill, and Remus on the Aventine Hill. The twins turned to augury (reading the auspices) and the result was in Romulus favour. When the spiteful Remus transgressed the sacred boundary of the Palatine, Romulus killed him. The twins' mother, Rhea Silva, was not just connected to the royal line of Alba Longa, she was actually the daughter of the usurped king of the city, Numitor. She was forced to become a Vestal virgin by the usurper, her uncle Amulius, who did not want any descendants.

This part of the legend was a later addition to connect the date of the foundation of Rome to the much earlier destruction of Troy as when the Romans became influenced by the Greeks they fancied to see themselves as descendant of the Trojans. In Greek mythology Aeneas, a Trojan hero,was saved twice during the Trojan war for an unknown destiny. The Romans continued the story. After a sojourn in Carthage and a stopover in Sicily Aeneas founded Lavinium in Latium. His son Ascanius founded Alba Longa and its royal dynasty.

Romulus is not said to have claimed rulership by divine right. Rather he seems to have acted as an augur and used religion to lay the foundation of the Roman state.