Andronikos IV Palaiologos

Andronikos IV Palaiologos or Andronicus IV Palaeologus (Greek: Ἀνδρόνικος Κομνηνὸς Παλαιολόγος, romanized: Andrónikos Komnēnós Palaiológos; 11 April 1348 – 25/28 June 1385) was the eldest son of Byzantine Emperor John V Palaiologos. Appointed co-emperor from 1352, he had a troubled relationship with his father: he launched a failed rebellion in 1373, usurped the throne in 1376–1379, and remained engaged in a bitter struggle with his father, John V, until his death in 1385. This civil war depleted Byzantium's scarce resources and greatly facilitated the Ottoman conquest of the Balkans, most notably through the cession of Gallipoli by Andronikos. He was also the father of John VII.

Source: Wikipedia — https://en.wikipedia.org/wiki/Andronikos_IV_Palaiologos