Who were Martin Sheen's parents?

Martin Sheen is Charlie Sheen's father. He is also the father of actor Emilio Estevez.
Carlos Irwin Estevez (better known as Charlie Sheen) is the son of Martin Sheen. As far as Ramón Gerardo Antonio Estévez (Martin Sheen), his father was a spanish immigrant, the name of which I do not know.