Medieval Karaite commentaries on incest prohibitions serve in this chapter as a lens for analyzing how notions of kinship and kin belonging developed in that setting. By examining what is required to become a relative with consanguineal or affinal kin belonging, the chapter explores the different notions of kinship and selfness that inform these legal trends and approaches. An innovative account is provided of the legal change that took place among the Karaites though the former half of the eleventh century as an outcome of changing perceptions of kinship, and shines a light on Karaite texts that have been largely ignored in modern scholarship, some printed here for the first time. Karaite authors discussed in the essay include Anan ben David, Ya’qub al-Qirqisani, Leṿi ben Yefet, Yeshu’ah ben Yehudah, Shelomoh ben David, and Yehudah Hadassi.