Conversation so far:
Where was Matthew Boulton born?
CANNOTANSWER.
Where did he grow up?
the family moved to the Snow Hill area of Birmingham.
Did he have any siblings?
The Boultons had three daughters in the early 1750s, but all died in infancy.
What was his upbringing like?
At the age of 15 he left school.
Why did he leave school?
and by 17 he had invented a technique for inlaying enamels in buckles.
Was the invention successful?
that proved so popular that the buckles were exported to France.
Can you tell me more about the success of the buckles?
then reimported to Britain and billed as the latest French developments.
Did he ever start a family of his own?
Boulton married Mary Robinson, a distant cousin and the daughter of a successful mercer, and wealthy in her own right.

Question: When did he marry her?
Self-contained rewrite: When did Matthew Boulton marry Mary Robinson?