Two Worlds, One Royal Family

Islam was founded by Heraclius. The first Islamic dynasty, the Umayyads, were overthrown by the Abbasid Dynasty, which was also founded by a Byzantine Emperor, Constantine V. The Seljuk Dynasty was taken over by the Mongol Khans. But who was the founder of the Seljuk Dynasty? I'm now researching a new essay on the link between the Byzantine Comnenos family and the Seljuk Turks.