John Paciorek was one of three brothers who played in the major leagues, but only he wound up with a batting average of 1.000. You see, he was 3-for-3 in his only major league game for the Houston Colt .45s (now the Astros) in 1963. Actually, the 18-year-old had five plate appearances in that game, but he managed to draw two walks in addition to his three hits. He scored four runs and had 3 RBI in the game on September 29 against the New York Mets.
John played in the minors until 1969,but never made it back to the big leagues.
Two of his brothers, Tom and Jim, also played in the majors, while a third brother, Mike, played for five seasons in the minors without reaching the big leagues.
Read more about John Paciorek at the link below from sportspagemagazine.com: