In ancient times, it was common for cousins to get married, and ancient people also liked it. For extended families, generally speaking, cousins are chosen to get married. Moreover, the ancient cousins did not find that their children were unhealthy. In addition, the ancients had no antipathy to the marriage of cousins, so they thought it was very correct for cousins to get married. Influenced by feudal thought, family was very important to ancient people. Children's marriage is generally the words of parents' lifelong matchmaker. As children, you can't disobey your parents, otherwise you are unfilial. Therefore, ancient people generally did not disobey their parents in marriage matters.
For the ancients with deep family values, the combination of cousins is actually the best development for the family. After all, they are all family. And if cousin and cousin get married, as a family, the bride price is not so important. And if the family has more property, it will eventually return to the family, which is an outsider who can't take advantage of it.
In fact, the ancient Japanese royal family and the Egyptian royal family were closely related to each other. Especially in the Egyptian royal family, there is even a tradition that brothers marry sisters and fathers marry daughters. Although consanguineous marriage was opposed or prohibited in ancient China, cousins were excluded. At the same time, this kind of marriage is actually a way to protect property. If the cousins of a large family get married, it is also a kind of help to the family and even brings them closer.