Biographies of Matsumura Nabe, grandson of Matsumura Sokon, are a challenge to write. Definitive works like McCarthy's translation of the Bubishi and Bishop's Okinawan Karate only mention him in passing. We know that he was a student of his grandfater, Matsumura Sokon, and was a strict traditionalist. In particular, he held to the old belief that the martial arts should be kept within the family. This stringent principle left him with only one student, his sister's son, Soken Hohan. According to Soken-san, Matsumura Sokon was Matsumura Nabe's only instructor which left him with the purest form of his grandfather's style.
Matsumura Nabe was the successor of Matsumura Sokon's family style, Uchinan Sui-de better known as Shuri-Te. Before his death, Matsumura Nabe gave his menkyo kaiden1 to Soken-san, making him the third-generation inheritor of his great-grandfather's style.
So why is information on Matsumura-san so hard to find? I believe the reason is the same as the reason why information about the early history of karate is difficult to confirm: No one wrote anything down. The early history of karate was largely oral. You hear statements like "I heard it from my instructor who was told by his instructor that . . .". So why does this pose a special challenge for Matsumura Nabe? Where some masters had many students to create an oral tradition around them, Matsamura Nabe had only one, Soken Hohan, so the information passed down about him is correspondingly meager.
1 A menkyo kaiden is a "certificate of advanced proficiency", the highest certificate awarded in many traditional Japanese martial arts styles.