Hmm, no one has ever asked me that question. People usually like to know about the 4 wives deal.
However if someone does ask you, say yes, he did. Ahan. Aisha (RA) was married to the Prophet (saw) because it was an honor for him and his daughter to be married to such a noble man. By marrying her, she was given the opportunity to learn Islam at such a young age and become one of the women leaders who not only helped spread Islam but also educate other women as she became na-mehram to the Prophet and was able to learn first hand.