Cassius Marcellus Clay Sr. is the father of this American former heavyweight boxer, younger brother to Muhammad, born in what year?
Cassius Marcellus Clay Sr.:  He was the father of three-time World Heavyweight Champion Muhammad Ali and Rahman Ali, and the grandfather of Laila Ali. Rahman Ali: Rahman Ali (born Rudolph Valentino Clay ; July 18, 1943) is an American former heavyweight boxer. Rahman Ali:  He is the younger brother of the late Muhammad Ali.
1943