Same-surname marriage

Same-surname marriage is the marriage of two people of the same surname. Historically, same-surname marriage was considered a taboo or prohibited in East Asian cultures.
China.
In ancient China, a policy against same-surname marriage was first instituted during the Western Zhou. In his interpretation of the "Book of Rites", philosopher Zheng Xuan compared same-surname marriage to zoophilia, and called it blasphemous; this indicated the seriousness of the Zhou dynasty's opposition to it. Confucianism opposed same-surname marriage because the school of thought that it would lead to weakness in reproduction of offspring. Both the "Guoyu" and the "Zuo zhuan" attributed the lack of same-surname couples to concerns with their offspring.
Although Confucianism opposed same-surname marriage, the taboo did not originate from Confucianism, and opposition to same-surname marriage later gained support outside Confucianism. Same-surname marriage formed part of the system of opposite-sex marriage in traditional Chinese marriage, where men and women within the same extended family were not permitted to marry, just as is the case in many patriarchal societies.
The Han dynasty did not have any statute prohibiting marriage between men and women of the same surname. Wang Mang's marriage to Empress Wang, the daughter of Wang Xian, indicates that same-surname marriage was not socially unacceptable during that period, if the couple do not share the same kin. Emperor Xiaowen reintroduced a law prohibiting same-surname marriage during the Northern Wei, with a usual penalty of capital punishment. Tang dynasty law continued to treat same-surname marriage as a crime, punishable by two years of imprisonment. The prohibition of same-surname marriage continued in the Ming and Qing dynasties; it was abolished towards the end of the Qing dynasty via judicial reforms, allowing men and women of the same surname and different kin to marry. In 1950, the People's Republic of China passed its New Marriage Law, which reduced restrictions on same-surname marriage to lineal blood relatives.
Vietnam.
Law during the early part of the Lê dynasty included a provision prohibiting same-surname marriage, similar to the legal provision in China. The phrase "" ("as long as the same surname") is often used.