Uthman Beg

Uthman Beg (, ) (reigned 1378–1435) was a late 14th and early 15th-century leader of the Turkoman tribal federation of Aq Qoyunlu in what is now eastern Turkey, Iran, Azerbaijan and Iraq.
Early beginnings.
He was born Baha-ud-Din Osman and was later given the nickname Qara Iluk or Qara Yuluk meaning "The Black Leech". Uthman Beg was the son of Fakhr-ud-Din Qutlugh, likely by his Greek wife, Maria, sister of Alexios III of Trebizond. He is estimated to have been born 1356. According to Byzantine and Aq Qoyunlu sources, he later married his maternal cousin, a daughter of Alexios III and his consort Theodora Kantakouzene. 
He was afraid of the intentions of his brothers, Ahmed and Pir Ali, when they joined Kadi Burhan al-Din of Sivas. He eventually killed his opponents and took over their territories in 1398 but retreated from Erzinjan on arrival of the Ottomans under Süleyman Çelebi.
Rise.
When Timur invaded the Caucasus and eastern Anatolia, the Aq Qoyunlu sided with him in support and fought alongside the Timurids against the Ottomans. For his services Uthman Beg was given Diyarbakır in 1402.