One of the fascinating aspects of the development of (western) marriage as a socio-religious-legal structure is the extent to which it derived legitimacy from symbolic performative acts by the parties to the marriage. (Those parties might be only the two people getting married, or their families might be considered "parties to the marriage" with required actions. It depended.) If the correct set of things were said and done (with "the correct set" altering over time and by local culture) then one was married.