JOHN XI  ., pope from 931 to 935, was the son of Marozia and the reputed son of Sergius III . Through the influence of his mother he was chosen to succeed Stephen VII. at the early age of twenty-one . He was the mere exponent of the purposes of his mother, until her son Alberic succeeded in 933 in over-throwing their authority . The pope was kept a virtual prisoner in the Lateran, where he is said to have died in 935, in which year Leo VII. was consecrated his successor .