Despite their significance for historical demographic research, a major limitation of Chinese genealogies is the relative lack of information on daughters, their husbands, and their descendants, which prevents an examination of how the boundary of family was extended through the marriage network. To fill this “hole” in Chinese genealogies, we use the genealogy of the Andong Kwôn clan, published in 1476, the oldest existing genealogy in Korea. Interestingly, more than 90 percent of those recorded in this Korean genealogy belong to the son-in-law line, revealing the importance of marriage networks for family formation until the late fifteenth century. By looking at the specific families that Andong Kwôn's daughters married into and the occupational titles of their husbands, we explore specific ways in which the family boundary was expanded to include the son-in-law lines.