Kanryo Higaonna (1853-1915)
Higaonna trained in Okinawa-te (the name given to Okinawan martial arts at the time) and then venturing to China where he trained for 13 years. He returned to Okinawa and developed a style ‘Naha-te’. The kata he taught were a combination of Okinawa-te principles and Chinese Kung fu. One of the many kata he developed and taught was Sanseru.
Chogun Miyagi (1888-1953)
Chogun was one of the two key students of Kanryo Higaonna. It is known that he altered the kata prior to establishing his Goju style. No one can be sure how much this was altered. Students were often taught kata to suit their bodies and skill levels, it is plausible that Higaonna taught Miyagi slightly different bunkai to suit his frame and later Miyagi adapted the kata to closer resemble his personalized bunkai.
Gogen Yamaguchi (1909-1989)
Gogen Yamaguchi was already a reputable karate-ka of Goju before he met its founder (Chogun Miyagi) around 1930. Miyagi became so impressed with Yamaguchi that he made him his successor for Goju in Japan.
While many karate styles incorporate Sepai, GKR derives its version from Japanese Goju (not the more kung-fu appearing Okinawan Goju Sepai).