Why is Emileo Estavez ' s name different from his family. Charlie Sheen is his brother correct?

Emilio Est�vez was born in New York City, the eldest child of actor Martin Sheen (Ram�n Gerardo Antonio Est�vez) and artist Janet (n�e Templeton). His siblings are Ram�n Luis Est�vez, Charlie Sheen, and Ren�e Est�vez. Unlike his brother, Emilio did not adopt his father's stage name.