Constantine I was briefly king of the Armenian Kingdom of Cilicia

Armenian Kingdom of Cilicia

The Armenian Kingdom of Cilicia , also known as the Cilician Armenia, Kingdom of Cilician Armenia or New Armenia, was an independent principality formed during the High Middle Ages by Armenian refugees fleeing the Seljuk invasion of Armenia...

 from 1298 to 1299. He was the son of Leo II of Armenia

Leo II of Armenia

Leo II , also Leon II, Levon II or Lewon II was the tenth lord of Armenian Cilicia or “Lord of the Mountains” , and the first king of Armenian Cilicia .During his reign, Leo succeeded in establishing Cilician Armenia as a powerful and a unified Christian...

 and Kyranna de Lampron

Queen Keran of Armenia

Keran was the wife of Leo II of Armenia. She was the daughter of Prince Hethum of Lampron. Born Anna, she was called Kir Anna beginning in 1270. This name was later shortened to Keran, or Guerane....

 and was part of the Hetoumid-family.

He helped his brother Sempad

Sempad of Armenia

Sempad, Smpad, Sambat, or Smbat ; 1277 – c. 1310) was king of the Armenian Kingdom of Cilicia, ruling from 1296 to 1298. He was the son of Leo II of Armenia and Kyranna de Lampron and was part of the Hetoumid-family....

 to usurp the throne in 1296, but turned against him two years later in 1298 to restore his older brother Hethum II

Hethum II of Armenia

Hethum II was king of the Armenian Kingdom of Cilicia, ruling from 1289 to 1293, 1295 to 1296 and 1299 to 1303, while Armenia was a subject state of the Mongol Empire...

. He assumed the throne for a year while Hethum recovered from his imprisonment. Shortly after Hethum's resumption in 1299, Constantine plotted to restore Sempad again, and both were imprisoned for the rest of their lives.