It's a little known fact that Johnny Weissmuller had a brother by the name of Peter who was a leading swimmer in his own right. On August 24th, 1923, Peter gave Johnny a hard fight to finish a close second in the final of the United States 100 yards championship which Johnny won in 54.6 seconds. In the 50 yards championship Peter finished third to Johnny and "Stubby" Kruger in that order. The winning time was 23.6 seconds.
Another little-known swimming brother was Ake Borg, twin brother of Arne Borg, the great Swedish 1500 meters swimmer, who in September, 1927, in one swim took 57.2 seconds off his own world 1500 record. Both brothers competed in the 1924 Paris Olympics 1500 meters event which was won by Australia's Andrew "Boy" Charlton in the World Record time of 20:06.6, a time that was an amazing 1:04.8 under the record. Arne Borg was second but his brother, Ake, progressed no further than the semi-finals.
Also at the 1924 Olympics, Johnny Weissmuller won the 100 meters freestyle in 59.0 secs. with two more brothers, Duke and Sam Kahanomoku, taking the 2nd and 3rd place spots respectively.