Some researchers argue that the prohibition against Suns' marrying Suns was largely a matter of incest taboo. In the early 18th century, all the Suns of a given generation appear to have been related within three degrees of consanguinity (siblings, first cousins, and second cousins). The custom of Suns' marrying commoners rather than Nobles may have been a preference rather than a requirement. Finally, while Swanton's interpretation claims that Nobles were also required to marry commoners, later researchers have questioned this idea. They have noted in particular a mistranslation of the primary sources and a misreading by Swanton. In other words, it could be that only Suns were required to marry exogamously, and this requirement may have been mainly a result of the taboo against incest.