"(...) During the Crusades, coexistence manifested itself in another way. Richard the Lionheart (king of England, 1189–1199) attempted to arrange a marriage between his sister and the brother of Saladin (the most famous hero of the Counter-Crusade and founder of the Ayyubid Dynasty). Intermarriage between Christians and Muslims was commonplace in Anatolia, and it was quite frequent between the Seljuk Turkish (who had conquered Byzatium in 1071, TN) and Byzantine elite.
At the same time, recent scholarship (...) has uncovered that many Byzantine women who married into the Seljuk Dynasty maintained their Christian religious practices and passed them onto their children (future Seljuk sultans), many of whom were baptized at the Hagia Sophia, the main cathedral in Constantinople. A consciousness of conversion did develop in the medieval period, but a thirteenth-century Cilician Armenian law code suggests that conversions to Islam were reversible."
This blog quotes from "Diversity in the Medieval Middle East - Inclusions, Exclusions, Supporters, and Discontents" by Rachel Goshgarian, Chapter 9 in Lucia Volk's The Middle East in the World: An Introduction (Foundations in Global Studies) (Routledge, 2015) on www.academia.edu;; source illustration www.quora.com