Died in 1252

Jan 23 Isabella Queen of Armenia the queen regnant of Cilician Armenia.
Feb 3 Sviatoslav III of Vladimir the Prince of Novgorod and Grand Prince of Vladimir-Suzdal.
Apr 6 Peter of Verona Saint Peter of Verona O.P. also known as Saint Peter Martyr, was a 13th-century Italian Catholic priest. He was a Dominican friar and a celebrated preacher. He served as Inquisitor in Lombardy, was killed by an assassin, and was canonized as a Catholic saint
May 30 Ferdinand III of Castile King of Castile from 1217 and King of León from 1230 as well as King of Galicia from 1231. He was the son of Alfonso IX of León and Berenguela of Castile. Through his second marriage he was also Count of Aumale. Ferdinand III was one of the most successful kings of Castile, securing not only the permanent union of the crowns of Castile and León, but also masterminding the most expansive campaign of Reconquista yet
Jun 9 Otto I Duke of Brunswick-Lüneburg the first duke of Brunswick-Lüneburg from 1235 until his death. He is called Otto the Child to distinguish him from his uncle, Emperor Otto IV
Jun 29 Abel King of Denmark Duke of Schleswig from 1232 to 1252 and King of Denmark from 1250 until his death in 1252. He was the son of Valdemar II by his second wife, Berengária of Portugal, and brother to Eric IV and Christopher I
Aug 1 Giovanni da Pian del Carpine one of the first Europeans to enter the court of the Great Khan of the Mongol Empire. He is the author of the earliest important Western account of northern and central Asia, Rus, and other regions of the Mongol dominion. He was the Serbian Primate and Archbishop of Antivari from 1247 to 1252
Nov 4 John of Wildeshausen a German Dominican friar, who was made a bishop in Bosnia and later the fourth Master General of the Dominican Order.
Nov 27 Blanche of Castile Queen of France as the wife of Louis VIII. She acted as regent twice during the reign of her son, Louis She was born in Palencia, Spain, 1188, the third daughter of Alfonso VIII, king of Castile, and Eleanor of England. Eleanor was a daughter of Henry II of England and Eleanor of Aquitaine