Authors:

In countries where there is no marriage, there is no duty between husband and wife; when marriage comes, husband and wife live together on account of attachment; and that kind of living together becomes settled after generations; and when it becomes so settled, it becomes a duty.

Swami Vivekananda (2015). “Karma Yoga: The Yoga of Action”, p.61, Advaita Ashrama
In countries where there is no marriage, there is no duty between husband and wife; when marriage comes, husband and wife live together on account of attachment; and that kind of living together becomes settled after