In the Animal Kingdom ... there are various types of Pair-Bondings ... some are for life, others happen, when the female is in heat, and the male just happens to be around ...
Now if you believe, in what Aristotle says about humans ... as being 'animals' of the 'social' kind ... then it matters very little, whether a couple ... is composed of a married pair ... or made up of a one night stand relationship ... both, in terms of sexual consummation, can lead to the birth of a child.
Marriage, my friend is a God Ordained Institution ... Marriage hath been Ordained ... so that there is Order and Sanity in Human Society ... Marriage is the Relationship, that "Distinguishes" Humans from the wild Animals.
God's Ordained ... is called Religion .... and the Logics and Philosophy's 'Ordered' is called ... Modern "Emancipation" !
Therefore ... What you do, is your own business ... my business, is to tell you about the difference, between Truth and Fallacy.