Penn was born to Jay Dee Penn, an Irish American and Loraine Shin, athird generation Korean-American. At the age of seventeen, Penn begantraining in Brazilian Jiu-Jitsu after being introduced to it by hisneighbor, Tom Callos. Callos had put up fliers in local gyms lookingfor people to train with, and B.J.'s father Jay Dee Penn had calledCallos and said his boys were interested. Callos then taught B.J. andhis brother what he knew. Shortly thereafter, B.J. moved to San Jose,California to begin training at AKA with Dave Camarillo and Bob Cooke,who he lived with and became close friends with. It was here during histime in San Jose that he decided to pursue a career in martial arts(albeit not mixed martial arts at the time).