Dimitrios Paleologos was probably born in 1407. He was the 5th son of Emperor Manuel II Paleologos and Eleni Dragatsis. From an early age he showed that he would develop into a great wound for Hellenism, which was living through tragic times. Ambitious and selfish, he was not satisfied with the island of Lemnos that his father granted him at the age of 15, but he fled to the Hungarian king Sigismund asking him for help against his brothers.
He remained in Hungary until 1427. In the meantime Manuel had died and had been succeeded by his eldest son John I. In November 1437 he accompanied the emperor to Ferrara where the council for the union of the churches was being held. He declared himself an antinotic and returned to Constantinople without the consent of his emperor brother.
As punishment he was stripped of command of Lemnos, but was eventually given the city of Mesimvria as he began to develop ties with the Turks. In April 1442 he attacked Constantinople with the reinforcement of the Turks provided by Sultan Murat, but was repulsed. He was imprisoned, but escaped and took refuge in Galata, the Genoese outpost opposite the City.
When John I died in 1448, Demetrius attempted a coup d'état to seize the city as his brother and heir to the throne Constantine IA was still in Mystras. The trickster Dimitrios failed again because of his mother.
To get rid of him, Constantine appointed him despot over half of the Despotate of Mystras. The other half of the Despotate had been received by his brother Thomas Paleologos. After the Fall of the City, the Palaeologist brothers faced the revolution of Dimitrios Kandauzinos with the help of the Turks, in 1454.
Immediately afterwards, however, Demetrius turned against Thomas, asking for the support of the Turks. The two brothers made peace when Thomas yielded to Demetrius' demands by granting him lands. The Turks, however, made the Palaeologians tax subjects. However, because they did not pay the tax due to internal disturbances, Muhammad campaigned in the Peloponnese.
Thomas Paleologos fled to Italy, and Demetrius, after a feigned resistance, surrendered Mystras to the Turks, without actually fighting, gaining personal rewards. The Sultan granted Demetrius the revenues from the Thracian city of Ainos and part of the revenues from Thassos and Samothrace. He lived in Ainos with his family until 1467.
But then he fell out of favor with Muhammad as he stole the taxes owed to the Turks, according to Sfrantzis. Mohammed took away all their possessions and Dimitrios and his relatives took refuge in Didymoteicho, mourning. Finally, Muhammad forgave him and settled him in Adrianople, giving him a small income. After the death of his daughter Eleni, in 1469, he became a monk with the name David. He died with the scheme in 1470, leaving behind only bad memories.