Who killed Remus and why?

According to Roman mythology, Remus was killed by his twin brother Romulus. There are several versions of the story explaining why Romulus killed Remus, but one of the most accepted versions suggests that the murder was a result of a dispute over where to found a new city, which would later become Rome. The brothers both descendants of the Trojan prince Aeneas were supposedly involved in a disagreement about the city's location. Upon selecting different sites they decided to seek the gods' approval through auspices signs or omens interpreted by birds.

Another factor that played into their conflict was the method of defining the city's boundaries. Remus, either in mockery of Romulus's efforts or flouting the sanctity of the city boundaries, jumped over the furrow his brother had plowed to mark the city limits. This act was considered an omen or a sacrilegious gesture undermining Romulus's claim. Insulted and believing his divine authority had been challenged Romulus killed Remus either in a fit of rage or under the notion that such a transgression must be punished.

The phrase "Romulus et Remus" is often mentioned when discussing the foundation of Rome, symbolizing the violent beginnings that lore suggests was integral to the city's history.