The 6th Duke had two sisters, both of whom married well.
The painting may have been done for a family who wanted their daughter to marry well.
Your only hope in this world is to marry well.
They hope that by being thrown into this society, she will marry well.
In the case of his sisters, they had used their status to marry well.
As for my wife, that was the best investment ever made by man; but 'in our branch of the family' we seem to marry well.
They seemed loving for a couple married well over twenty years.
She seems to have married well, and may have had a daughter.
He married well, mind you, but his wife proved unable to have children.
He'd marry well, but know where his other desires lay.