Brotherly Brawlers & Sisterly Strikers: Inside the UFC's Top Siblings
Nick Diaz and Nate Diaz
Antônio Rodrigo Nogueira and Antônio Rogério Nogueira
Jim Miller and Dan Miller
Anthony Pettis and Sergio Pettis
Valentina Shevchenko and Antonina Shevchenko
Kamaru Usman and Mohammed Usman
Gilbert Burns and Herbert Burns
Joe Lauzon and Dan Lauzon
Ken Shamrock and Frank Shamrock (adopted brothers)
Alexander Emelianenko and Fedor Emelianenko (Fedor fought extensively in Pride FC, but Alexander also had fights in the UFC, and Fedor is widely associated with MMA's top promotions.)