Kiddushin 4b Gender Identity and Exchanging Rings - כי יקח ולא כי תקח

Gender is not about how an individual chooses to identify; nor is it only about individuals’ physiology. Gender is about an individual’s essence, their feelings, their spiritual beings, their energies, and their respective capacities. Relationships are only possible between individuals with separate identities. Kiddushin is only possible between individuals of separate genders. Sources