Aisha was the daughter of Muhammad's close friend Abu Bakr. She was initially betrothed to Jubayr ibn Mut'im, a Muslim whose father, though pagan, was friendly to the Muslims. When Khawlah bint Hakim suggested that Muhammad marry Aisha after the death of Muhammad's first wife (Khadija), the previous agreement regarding marriage of Aisha with ibn Mut'im was put aside by common consent.
Aisha was six or seven years old when betrothed to Muhammad. Traditional sources state that she stayed in her parents' home until the age of nine when the marriage was consummated with Muhammad, then 53, in Medina, with the single exception of al-Tabari, who records that she was ten. Both Aisha and Sawda, his two wives, were given apartments adjoined to the Al-Masjid al-Nabawi mosque.
http://en.wikipedia.org/wiki/Muhammad's_wives