Ostrogski was one of the greatest Ruthenian

Ruthenians

The name Ruthenian |Rus']]) is a culturally loaded term and has different meanings according to the context in which it is used. Initially, it was the ethnonym used for the East Slavic peoples who lived in Rus'. Later it was used predominantly for Ukrainians...

 prince

Prince

Prince is a general term for a ruler, monarch or member of a monarch's or former monarch's family, and is a hereditary title in the nobility of some European states. The feminine equivalent is a princess...

ly families of the Grand Duchy of Lithuania

Grand Duchy of Lithuania

The Grand Duchy of Lithuania was a European state from the 12th /13th century until 1569 and then as a constituent part of Polish-Lithuanian Commonwealth until 1791 when Constitution of May 3, 1791 abolished it in favor of unitary state. It was founded by the Lithuanians, one of the polytheistic...

.

They were most likely of Rurikid stock and descended from Sviatopolk II of Kiev

Sviatopolk II of Kiev

Sviatopolk II Iziaslavich was supreme ruler of the Kievan Rus for 20 years, from 1093 to 1113. He was not a popular prince, and his reign was marked by incessant rivalry with his cousin Vladimir Monomakh...

. Some scholars however claim their descent from Galicia-Volhynia line of Rurikid dynasty. Vasilko Romanovich (c.1256-1282) Prince of Slonim

Slonim

Slonim is a city in Hrodna Voblast, Belarus, capital of the Slonim District. It is located at the junction of the Shchara and Isa rivers, 143 km southeast of Hrodna. The population in 2008 was 50,800.-Etymology and historical names:...

 may have been grandfather of Prince Daniel Ostrogski. The probable progenitor of this family was Prince Danylo Dmytrovych (or Danylo Wasilijewicz), who received Ostroh

Ostroh

Ostroh is a historic city located in Rivne Oblast of western Ukraine, located on the Horyn River. Ostroh is the administrative center of the Ostroh Raion and is itself designated as a special administrative subordination within the oblast...

 from Liubartas, King of Galicia-Volhynia and son of Grand Duke of Lithuania Gediminas.