"Another remarkable discovery was learning that Cyan Chotoku (1870-1945), another of Okinawa’s greatest karate masters, was Motobu’s cousin. According to Motobu Chosei, “Cyan was born as a Motobu but became a Cyan family member to maintain the Cyan family name. In Okinawan noble families, this was not unusual. First sons had to maintain their own family’s names to preserve the family’s lands and entitlements. Later born sons would often be adopted or marry into other noble families in which there were no sons. Motobu Choki and Cyan Chotoku, who were about the same age, often practiced karate together.” (Setting the Record Straight,” 3rd Quarter issue journal 2001, pages 12/13)"
I can't speak to the veracity of the above quote. I just found it.