Sean Aloysius O'Brien was an important leader of labor unions in the early 20th century, and an ancestor of Miles O'Brien.
O'Brien led the anthracite strike of 1902, a bitter controversy that lasted for eleven months, and only ended when all of the workers' demands were met. Unfortunately, O'Brien himself was killed barely a week before the strike concluded — his body was found in the Allegheny River with 33 bullets in him (possibly 34...). He had one of the largest funerals in western Pennsylvania history.
Miles O'Brien would later recall his ancestor with pride, noting that he wasn't just a hero, he was "a union man." (DS9: "Bar Association")
- The actual leader of the 1902 anthracite strike was United Mine Workers' president John Mitchell.
As Miles and Keiko O'Brien prepared for the birth of their son, one name Miles proposed was Sean, perhaps in honor of this early ancestor. Keiko reminded him that Sean means "swamp" in the Bajoran language, and the couple eventually settled on the name Kirayoshi. (DS9: "Let He Who Is Without Sin...")