On Jedha, it's traditional for rich families to arrange marriages for their children -- furthermore, it's traditional to arrange for younger children (i.e. not the family's primary heir) to marry Guardians of the Whills. Marrying a child off to a Guardian signifies piety and devotion to Jedha/the Guardians, and a Guardian being married off to a non-Guardian often ends up providing the Temple with more money.

Baze is the youngest Malbus son and doesn't get along well with his father. He's not quite surprised when he ends up the promised husband of a Guardian. But Chirrut is...not what he expected.

(Happy ending please <3)