Account to myth, where did the twins come from

A powerful ring cut a boy in half, and he became two.

Romulus and Remus are recorded in Roman mythology as the founders of the city Rome. Legend has that the twins were born around 770BC, the sons of a mortal priestess, Rhea Silvia, and the Roman god of war, Mars. The boys were abandoned at birth and thrown into the River Tiber in a cradle