I want to be the white man's brother, not his brother-in-law.

The line contrasts genuine fraternity with a merely formal or reluctant connection. “Brother” implies equal standing, mutual affection, and shared civic belonging; “brother-in-law” suggests an imposed tie—related only through legal or social arrangement, potentially kept at arm’s length. Attributed to King, the sentiment fits his broader insistence that desegregation and civil rights were not simply about access or legal compliance but about creating a “beloved community” grounded in real interracial solidarity. The quip’s bite lies in exposing how token integration can preserve emotional distance and hierarchy even while appearing to concede relationship.