The Ming dynasty author Shen Defu(沈德符) wrote in "Miscellaneous Musings of the Humble Broom Bookroom":

Recently, the "oath sons" phenomenon is catching on. The situation is that some strong adult males have a strong sex drive, so they spend a great deal of money to marry extremely good-looking youths. They establish the bond of the quilt and the coverlet with them. Those arrangements in which the 'father' lives apart and houses several youths in various secondary lodgings are foremost in disorder and sin. I heard this practice started with pirates, as in: The Ocean forbids the presence of women in the crew. Ships with women would be sunk. So they replace (women) with male favorites; and they honor the great and strong (pirates) by addressing (them) as "oath father" .

The Fujianese takes male-male eroticism very seriously. Regardless of his social standing, each man bonds with another man of his own social class; the older one is known as the "sworn older brother" and the younger one is known as the "sworn younger brother". When the older brother enters the home of the younger, the younger brother's parents love him as a son-in-law. In the future, when the younger brother starts a business or marries a wife, the older brother helps pay for the expenses. Those who love each other thus still lie together as spouses after the age of 30.