Queen Blanche not the Regent

Louis IX, King of France, reigned from 1226 until 1270. Louis was twelve years old when he first became King.
His mother Queen Blanche (Blanche of Castile) was the regent. She had Louis crowned within a month of his father's death in Reims.

Suppose Blanche of Castile was not the regent. Who would be regent for King Louis IX?
 
Philip I, Count of Boulogne (1201-1235) was a French prince. He was the son of Philip II, King of France and younger half-brother of King Louis VIII.
Suppose Philip I, Count of Boulogne lives many years beyond 1235. He is the regent for King Louis IX.
 
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