The Vatican has issued a 40-page doctrinal document called "One Flesh – In Praise of Monogamy," signed by Pope Leo XIV and authored by Cardinal Víctor Manuel Fernández, reaffirming that marriage is a lifelong, exclusive union between a man and a woman.The document distinguishes polygamy from polyamory, addresses challenges discussed in Vatican assemblies in 2023 and 2024, and responds to increasing polygamy in Africa and the rise of polyamory in Western societies.Cardinal Víctor Manuel Fernández states that the final chapter on "conjugal charity" communicates the central message and underscores the importance of marriage's unity, exclusivity, and openness to children.