Conversation so far:
When did John Lennon meet Cynthia Lennon?
Lennon met Cynthia Powell (1939-2015) in 1957.
Did they meet while attending school?
in 1957 when they were fellow students at the Liverpool College of Art.
How old were they when they met?
CANNOTANSWER.
How long before they married?
The couple wed on 23 August at the Mount Pleasant Register Office in Liverpool.
How long did their marriage last?
November 1968, with Lennon giving her PS100,000 ($240,000 in US dollars at the time), a small annual payment and custody of Julian.
Did Cynthia ever remarry?
CANNOTANSWER.

Question: Did she only have one child with Lennon?
Self-contained rewrite: Did Cynthia Lennon only have one child with John Lennon?