Vaidotas or Wojdat was a son of Kęstutis

Kestutis

Kęstutis was monarch of medieval Lithuania. He was the Duke of Trakai and governed the Grand Duchy of Lithuania, 1342–82, together with his brother Algirdas , and with his nephew Jogaila...

, Grand Duke of Lithuania. In reliable historical sources he is mentioned only twice.

According to the chronicles of Wigand of Marburg

Wigand of Marburg

Wigand of Marburg was a German herald of the Teutonic Knights in Prussia and one of the notable chroniclers of the Middle Ages.Wigand expanded upon the earlier work of Nikolaus von Jeroschin...

, he was the commander of the garrison

Garrison

Garrison is the collective term for a body of troops stationed in a particular location, originally to guard it, but now often simply using it as a home base....

 of the newly-built Kaunas Castle

Kaunas Castle

Kaunas Castle is located in Kaunas, Lithuania. Archeological evidence suggests that it was originally built during the mid-14th century, in the Gothic style. Its site is strategic – a rise on the banks of the Nemunas River near its confluence with the Neris River...

 during a three-week-long siege in April 1362. After strong resistance the castle was taken over and then destroyed. Vaidotas with 36 men tried to break through, but was taken prisoner. The defeat was one of the largest and important military victories of the Teutonic Knights

Teutonic Knights

The Order of Brothers of the German House of Saint Mary in Jerusalem , commonly the Teutonic Order , is a German medieval military order, in modern times a purely religious Catholic order...

 in the 14th century against Lithuania.

From a document by his brother Vytautas the Great

Vytautas the Great

Vytautas ; styled "the Great" from the 15th century onwards; c. 1350 October 27, 1430) was one of the most famous rulers of medieval Lithuania. Vytautas was the ruler of the Grand Duchy of Lithuania which chiefly encompassed the Lithuanians and Ruthenians...

 from 1401 it is known that Vaidotas and his brother Tautvilas Kęstutaitis were given to rule Navahrudak equally. His further fate is unknown.

Because of very limited historical sources, Vaidotas is sometimes confused with Vaidutis (Waydutte), son of Butautas and grandson of Kęstutis. Some historians also argue that Butautas and Vaidotas were the same person and their names are different because of a different dialect. Further confusion is introduced by Bychowiec Chronicle

Bychowiec Chronicle

The Bychowiec Chronicle named the Letopis of the Grand Dukes of Lithuania is an anonymous 16th century chronicle of the Grand Duchy of Lithuania. Although one of the least reliable sources of the epoch, it is considered the most complete redaction of the Lithuanian Chronicles...

, an unreliable chronicle from the 16th century, which claims that Vaidotas died in his youth in Lithuania.