Demetrius was a son of King Alexander I of Imereti (died 1389), who had broken away from the Kingdom of Georgia during Timur's invasions of that country in 1387. After his uncle, King George I, was killed in 1392, Demetrius was carried away by another his uncle, Constantine, to seek refuge in the Caucasian mountains. They were able to return to Imereti in 1396, when Constantine was proclaimed king. He died childless in 1401, leaving the throne to the young and weak Demetrius. His accession was prevented, however, by King George VII of Georgia, who, once freed from a protracted war with Timur, invaded Imereti. The Dadiani of Mingrelia and Imeretian nobles captured Demetrius and delivered him to George, who treated him with consideration and sent him to a safe retreat in Somkhiti, in Kartli. Alexander I of Georgia, who married Demetrius's sister Tamar c. 1415, restored him to Imereti as a vassal "eristavi" ("duke"). He remained loyal to the Georgian crown and died in 1455.