Castro is a percussionist of Puerto Rican descent and was born and raised in New York City. His father Hector Castro, played the keyboard in a Latin style and his stepfather George Cordero gave his stepson his first pair of congas when he was five years old and drum set as well. Along with the congas the junior Castro played the bongos, which he grew up performing in schools. Unlike many of his "Latin brothers", Castro listened and played percussion not to just Latin music but jazz, rock, classical, and anything else that could have percussion added in. He claims not to have planned on becoming a studio musician, only that he wanted to play music. Whether this meant live or in recordings, he didn't care as long as he got to play.
Castro later began to make money with different gigs in New York, which he called a "playground" at the time, when he was around 14 or 15. This lasted him until he graduated from The High School of Music & Art in 1974.
After graduation Castro went to Mannes college with a scholarship that a high school teacher had helped him to acquire. However, he quickly tired of college and dropped out. He found a job at a famous drum shop in New York where he worked for three or four months.
Through this store, Castro got a big break with Melissa Manchester who had a hit at the time, "Midnight Blue". After Castro did a couple of tours with her, Manchester moved to Los Angeles. Castro, 19 at the time, did not want to give up this opportunity and left New York City to follow Manchester and his career. Her producer later introduced Castro to fellow producer Richard Perry. Perry had Castro play at a Diana Ross session, which is where he met Jeff Porcaro. Porcaro got Castro a gig with Boz Scaggs, who had just released Silk Degrees. Scaggs toured all around the world with Castro as his percussionist. This tour is what landed Castro the Toto gig and also kick-started his Los Angeles session legacy.
Because he is a freelancer, Castro is called on by many artists and bands to record. He claims to enjoy this freedom, saying that the members of Toto did him a favor by not asking him to join permanently; "I didn't get handcuffed or chained down". The artists and bands that Castro has worked many U.S. musical artists as well as many Japanese, Italian, English, German artists.
Castro has recorded with Fleetwood Mac and performed on The Dance tour in 1997. Castro was also a part of the Fleetwood Mac contingent that surprised former President Bill Clinton on January 6, 2001. Castro toured with Stevie Nicks in 2007 and 2011 for her "In Your Dreams" tour, and toured with Noel Gallagher's High Flying Birds in 2011 and 2012.
In 2014, Castro was invited by producer Gerry Gallagher to record with Latin rock legends El Chicano and is featured on percussion on several songs on Gallagher's most recent studio album due out in 2017.
On his first tour with Boz Scaggs, Castro courted singer Paulette Brown. They became husband and wife and had two children. Their son, Tyler, plays the drums and their daughter Christina sings and enjoys the culinary arts. Paulette died in 1998 of lung cancer after a three-year illness. Castro remarried Chie Yamamura from Osaka, Japan. They were introduced while Castro was touring the Blue Notes in Japan with the Joe Sample Trio.