Complex sentence: The JBC has joined the NBA (the current WBA) as of January 7,1954, and the WBC since the rematch of Johnny Famechon vs. Fighting Harada in January 1970.
Split into simpler sentences: The JBC has joined the NBA (the current WBA) as of January 7,1954. They have also joined the WBC since the rematch of Johnny Famechon vs. Fighting Harada in January 1970.