Conversation so far:
Was John married?
Dee was married three times.
did he have children?
Dee was married three times and had eight children.
who was his first wife?
He first married Katherine Constable in 1565; she died in 1574 and their union resulted in no children.
who was his second wife?
His second (also childless) marriage to an unknown woman lasted only a year until her death in 1576.
did they have children?
His second (also childless) marriage.
did John attend school?
CANNOTANSWER.

Question: who was John's third wife?
Self-contained rewrite: who was John Dee third wife?