Were there female relatives of the Prophet Muhammad among the besieged Qurayza?

Three members of the Jewish tribe Qurayza, two brothers and their relative, left the tribe's besieged fortress hours before Qurayza's unconditional surrender to the Prophet Muhammad, thereby saving their lives, their families, and their orchards. According to a rather widespread account, the three had become convinced of the veracity of Muhammad's mission. But there is a more cogent explanation for their survival: according to Ibn al-Kalbī's Kitāb al-Mathālib, the two brothers were married to two sisters who were Muhammad's third cousins.