Development of strategies for induction of HIV-1 broadly neutralizing antibodies (bnAbs) by vaccines is a priority. Determining the steps of bnAb induction in HIV-1-infected individuals who make bnAbs is a key strategy for immunogen design. Here, we study the B cell response in a bnAb-producing individual and report cooperation between two B cell lineages to drive bnAb development. We isolated a virus-neutralizing antibody lineage that targeted an envelope region (loop D) and selected virus escape mutants that resulted in both enhanced bnAb lineage envelope binding and escape mutant neutralization—traits associated with increased B cell antigen drive. Thus, in this individual, two B cell lineages cooperated to induce the development of bnAbs. Design of vaccine immunogens that simultaneously drive both helper and broadly neutralizing B cell lineages may be important for vaccine-induced recapitulation of events that transpire during the maturation of neutralizing antibodies in HIV-1-infected individuals. Display omitted •The steps in induction of HIV-1 broadly neutralizing antibodies have been mapped•The steps involve cooperation between two distinct B cell antibody lineages•One lineage induced escape mutants with enhanced binding to bnAb precursors The molecular identification of two B cell lineages that cooperate for the generation of broadly neutralizing antibodies offers new insights into the design of antigens that can be used to elicit protective immunity to HIV infection.