Research consistently documents the wide-ranging strains of family member incarceration, but less is known about the different ways family members work together to manage these strains or the additional strains stemming from this coordination. We use in-depth interview data from the Jail and Family Life Study, drawing on longitudinal interviews with 69 mothers and 85 romantic partners of incarcerated men, to understand the symbiotic harms of jail incarceration for families. We find that the strains of family member incarceration engender reactionary brokering, a concept we define as the collaborative work family members engage in (with each other and occasionally with institutional actors) to manage strains generated by the sudden absence of a loved one. We uncover three primary types of reactionary brokers—exhaustive, concentrated, and bounded—alongside a group of monitors who oversee but are largely excluded or exempt from the brokering role. We also trace the socially patterned processes that shape these roles. Although reactionary brokering can provide critical support for families, it also generates substantial new strains, particularly for families with harmonious relationships that facilitate brokering. The concept of reactionary brokering illuminates how family members experiencing the same strain—in this case, incarceration—arrive at divergent brokering roles that can create new inequalities.