Richard Hart, born James Capone, was the oldest brother of gangster Al Capone and a Prohibition agent.
Hart in the Timeless Universe
When Al Capone became a major criminal, James Capone fled and changed his name to Richard Hart to distance himself from his brother. Hart became a Prohibition agent, as well as a husband and father. His new family does not know of his relation to the Capone's.
When Eliot Ness is killed, Lucy Preston, Rufus Carlin, and Wyatt Logan all turn to Richard Hart for help with getting Al Capone arrested. Hart is very against the plan, but eventually agrees to go and arrest Capone.
Hart is recognized by Frank Galluccio, who leads the group to Capone. Capone is ecstatic to meet Hart again after so many years, but this joy quickly fades after Hart tells Capone that he's here to arrest him. Guns are drawn. Capone points a gun at Rufus, claiming that killing Rufus is the other favor he owes Flynn. Hart points a gun at Capone, and so does Wyatt. Frank Galluccio, one of Capone's top men, points a gun at both Lucy and Rufus. Capone shoots Rufus, but is then fatally shot by Hart. In the altered timeline, Capone dies on March 13, 1931.
James Vincenzo Capone at Wikipedia