I was recently doing research for a patron on marriage law of the People’s Republic of China (PRC or China), and I found the method used by the Chinese marriage law in calculating degrees of kinship very unique. Marriage law usually prohibits blood relatives within certain degrees of blood relatedness to get married. First cousins, for example, who are often fourth degree relatives, are prohibited in many jurisdictions from getting married. The PRC Marriage Law, which also bans cousin marriage, prohibits marriage between relatives by blood “up to the third degree of kinship” (art. 7(1)). So, how does the PRC Marriage Law calculate the degrees of kinship?
The degrees are calculated primarily based on the number of generations. For lineal relatives, there are as many degrees as generations, including the person in question. Therefore, there are two degrees between a person and his or her father, and three degrees between that person and his or her grandfather. (HONGXIA LIAO, HUNYIN JIATING FA GAILUN 38 (2014).)
In computing degrees between collateral relatives, the degrees between each person and the common ancestor must first be calculated, using the same method used to calculate degrees between lineal relatives. If the number of degrees in the two lines is equal, that number is considered the number of degrees between the two persons. If the number of degrees in the two lines is unequal, the number of degrees of the longer line will be the number of degrees between the two persons. (Id. at 38–39.) Therefore, under the PRC Marriage Law, siblings are considered second-degree relatives, because there are two degrees between each of them and the parent. First cousins are third-degree relatives, because there are three degrees between each of them and the common ancestor, the grandparent.
Note that the degrees of kinship under Chinese law do not necessarily reflect the distance of a blood relation. Although the distance of blood relation between an individual and his or her first cousin is further than that with his or her uncle or aunt, the uncle or aunt is also third degree relative under the PRC Marriage Law: there are three degrees from the individual to the common ancestor (his or her grandparent) and two degrees from the uncle to the grandparent. Since the number of degrees in the two lines is unequal, the degrees in the longer line (three degrees) will be considered the number of degrees between the individual and the uncle or aunt.