Benjamin's father is European and his mother is Quechuan. In 1969, when Benjamin was a child living in San Francisco his mother took him to participate in the Native-American Occupation of Alcatraz.
Today, Benjamin is an active supporter of such Native-American causes as the American Indian College Fund and We Shall Remain, a mini-series and multi-media project, narrated by Bratt, that establishes Native history as an essential part of American history from PBS' acclaimed series American Experience.
He was also in the film Follow Me Home, 1996 film directed by his brother. It explores spiritual and intercultural race relations through the lives of four artists, one African American, one Native-American and two Latin-American cousins. Bratt has for years been a strong supporter and board member of San Francisco Bay Area's Friendship House Association of American Indians and Native-American Health Center.