Most African captives were prisoners of war or social outcasts, not kin.

Evidence

African elites did not typically sell their own kin. Captives tended to be “culturally and ethnically alien to those who enslaved them,” writes the historian James Campbell, the author of Middle Passages: African American Journeys to Africa, 1787–2005.15 About half the captives were prisoners of war, according to Rawley and Behrendt. Another third were people labeled as criminals, undesirables, or outcasts and treated with disdain (similar to how the English regarded indentured servants forcibly shipped to their North American colonies and Australia in the seventeenth and eighteenth centuries). The 20 percent remaining, Rawley and Behrendt estimate, were victims of kidnapping. — Nikole Hannah-Jones et al., The 1619 Project, 279