She is usually a willing participant in the relationship and may be of any social status.
The harem of the palace did house the Sultan's wives and concubines, but it typically also housed all of the women of the palace, including his mother, sisters, aunts, and cousins.
Queen Catherine de' Medici resented her husband's dalliances with his much older concubine, Diane de Poitiers.
The senator's wife was indignant, barely containing her rage when she confronted her husband about the secret series of concubines that he had.
my golly jean, theres a concubines outside our house, whatever should we do?