This paper argues that the milk relations of Qabīṣa ibn Dhuʾayb al-Khuzāʿī (d. ca. 87/706) and ʿAbd al-Malik ibn Marwān (r. 65–86/685–705) factored into the former’s career during the latter’s caliphate. Qabīṣa was granted several administrative responsibilities during the caliphate of ʿAbd al-Malik ibn Marwān. His son, Isḥāq ibn Qabīṣa, had a successful career under ʿAbd al-Malik’s sons, al-Walīd (r. 86–96/705–15) and Hishām (r. 105–25/724–43), which culminated in holding the desirable post of governor. Previous scholars have noted that Qabīṣa and ʿAbd al-Malik were brothers-in-law—a marital tie which, as this paper shows, is not the only one attested between the two families. However, the fact of their milk relations, which is not found in the mainstream Muslim sources, has thus far not received the scholarly attention it deserves. The account of ʿAbd al-Malik’s and Qabīṣa’s nursing ties, I contend, provides a plausible explanation for Qabīṣa’s illustrious career, as well as contributing to our knowledge of the close relations shared by their tribes, Quraysh and Khuzāʿa, in the pre- and early Islamic periods. That Qabīṣa ibn Dhuʾayb and ʿAbd al-Malik ibn Marwān were closely connected individuals is evident both from the marital links between their families and from the numerous appointments that Qabīṣa and his son received during the caliphates of ʿAbd al-Malik and his sons. The long history shared by the tribes to which Qabīṣa and ʿAbd al-Malik belonged provides another piece of supporting evidence for their amicable relations. However, without the missing link of the milk relationship of Qabīṣa and ʿAbd al-Malik, we are left in the dark as to why it was particularly Qabīṣa and his family that received this favorable treatment. The importance of Qabīṣa’s and ʿAbd al-Malik’s milk kinship is enhanced by the fact that evidence of its existence is rare, being found, to the best of my knowledge, in only one source. This paper thus demonstrates that consulting a wide array of primary sources in order to find unique accounts is a promising work method for elucidating the factors influencing political appointments in the early Islamic period.