Originally from Honolulu, Hawaii, Mr. Castro began training with the late William K. S. Chow who brought him up into the black belt ranks.

In the early 1960's, Mr. Castro moved to the U.S. mainland settling in the San Francisco Bay Area where he began to teach and spread Shaolin Kenpo Karate producing many top blackbelts who became masters in their own right.

In the intervening years, Mr. Castro also promoted numerous tournaments and demonstrations.

Ralph Castro was entered in the 1982 Inside Kung Fu Yearbook. In 1985, his story was told in Official Karate and he was pictured on the cover. He was featured on the cover of Karate Kung Fu in 1987. Black Belt magazine placed Mr. Castro on its June cover in 1988 and entered him into its Black Belt Hall of Fame that same year. In 1989, Mr. Castro was entered in Black Belt's yearbook.

Mr. Castro was an AAU vice-president as early as 1971 - 1972. In addition to this, he maintained active membership in Mr. Parker's International Kenpo Karate Association from 1958 to 1982.

In 1981, Mr. Castro founded the International Shaolin Kenpo Association of which he is the current President. He was also active within ATAMA serving as the National Board's Vice-President in 1985 and President in 1986-1988.