question: What is the date of birth of John I, Duke Of Brunswick-Grubenhagen's mother?
context: [["John I, Duke of Brunswick-Grubenhagen", ["John I, Duke of Brunswick-Grubenhagen (born: before 1322; died: 23 May 1367)", "was provost of the St. Alexandri Minster in Einbeck.", "He was the son of Duke Henry", "I \"the Marvelous\" of Brunswick-Grubenhagen and his wife Agnes of Meissen, daughter of Margrave Albert II of Meissen."]], ["Clara of Brunswick-Wolfenb\u00fcttel", ["Clara of Brunswick- Wolfenb\u00fcttel( 16 November 1532 in Wolfenb\u00fcttel \u2013 23 November 1595 at Herzberg Castle), was a princess of Brunswick- Wolfenb\u00fcttel by birth.", "She was abbess of the secular Gandersheim Abbey and later Duchess of Brunswick- Grubenhagen by marriage."]], ["William, Duke of Brunswick-Grubenhagen", ["William of Brunswick- Grubenhagen( \u2013 1360) was a Prince of Brunswick- Grubenhagen."]], ["Agnes of Meissen", ["Agnes of Meissen (born before 1264 \u2013 died after September 1332) was a noblewoman, the daughter of Albert II, Margrave of Meissen and his wife Margaret of Sicily.", "Agnes was married with Henry I \"the Marvelous\" of Brunswick-Grubenhagen, in 1282.", "They had 16 children:"]], ["Ernest III, Duke of Brunswick-Grubenhagen", ["Ernest III of Brunswick- Grubenhagen- Herzberg( by a different counting: Ernest IV; 17 December 1518 in Osterode am Harz \u2013 2 April 1567 in Herzberg Castle, Herzberg am Harz), was a member of the noble family of Guelph and a duke of Brunswick- Grubenhagen."]], ["Henry IV, Duke of Brunswick-Grubenhagen", ["Duke Henry IV of Brunswick Grubenhagen( 1460 \u2013 6 December 1526, Salzderhelden, now part of Einbeck) was a member of the Guelph dynasty and was Prince of Brunswick- Grubenhagen."]], ["Ernest I, Duke of Brunswick-Grubenhagen", ["Ernest I of Brunswick- Grubenhagen( \u2013 9 March 1361) was Prince of Brunswick- Grubenhagen."]], ["Melchior of Brunswick-Grubenhagen", ["Melchior of Brunswick- Grubenhagen( died 1381 or 1384) was a German aristocrat, prince- bishop of Osnabr\u00fcck from 1369, and then prince- bishop of Schwerin from 1376 to 1381.", "He was the son of Henry II, Duke of Brunswick- Grubenhagen."]], ["Anna of Brunswick-Grubenhagen-Einbeck", ["Anna of Brunswick- Grubenhagen- Einbeck( 1414 \u2013 4 April 1474) was a daughter of Duke Eric I of Brunswick- Grubenhagen and his wife, Elisabeth of Brunswick- G\u00f6ttingen.", "Anna's first marriage was with Duke Albert III of Bavaria.", "They had the following children:", "After Albert's death, she married Duke Frederick III of Brunswick- Calenberg- G\u00f6ttingen.", "This marriage remained childless."]], ["Eric I, Duke of Brunswick-Grubenhagen", ["Eric I, Duke of Brunswick- Grubenhagen nicknamed\" the winner\"( \u2013 28 May 1427), ruled the Principality of Grubenhagen, a part of the Duchy of Brunswick- L\u00fcneburg."]]]
supporting_facts: [["John I, Duke of Brunswick-Grubenhagen", 3], ["Agnes of Meissen", 0]]
evidences: [["John I, Duke of Brunswick-Grubenhagen", "mother", "Agnes of Meissen"], ["Agnes of Meissen", "date of birth", "1264"]]
answer: 1264