Between the close of The Prime Minister and the opening of The Duke's Children, the Duchess of Omnium died, leaving to the Duke the care of his three children. The eldest, Lord Silverbridge, had been sent down from Oxford as a result of a certain amount of red paint applied to the front of the Dean's house; the second son, Lord Gerald Palliser, was doing indifferently well at Cambridge; Lady Mary Palliser, the only daughter, was determined on what seemed to her father an unsuitable marriage.
Before the story opens, while the family were in Italy, young Frank Tregear, a friend of Lord Silverbridge, had joined them, and with the Duchess' consent had become engaged to Lady Mary. Of this the Duke knew nothing, until, through the insistence of Mrs. Finn, Lady Mary's chaperone, Frank asked for her hand. The Duke was enraged at the temerity of this young man who, without place, position or money, should dare to look so high. The engagement was declared impossible and the young suitor was forbidden to see or communicate with Lady Mary. The daughter conceded her father's authority but made it quite clear that she still considered herself bound by her promise to Frank.
Meanwhile Lord Silverbridge became a partner with a certain Major Tifto in the ownership of a race horse called "Prime Minister," which failed to win the Leger, as a result of Tifto's treachery, and with a loss to Silverbridge of £70,000. The Duke paid the debt on his son's promise to forsake the turf and devote himself to his duties as MP from the family borough. He urged an early marriage, thinking it would steady his son. At about this time a beautiful and talented American girl, Isabel Boncassen, had come to London with her parents and had been received into the best society. Lord Silverbridge met her and fell deeply in love. Although the Duke was attracted to her charm and beauty, and had a sincere respect for her scholarly father, he was strongly opposed to the marriage of the heir to a dukedom and the granddaughter of an American laboring man. Like Lady Mary, Lord Silverbridge had something of the self-will and tenacity of purpose of their mother, and would not he denied. It was not long before his son's insistence and Isabel's charm had vanquished the Duke's prejudice, and when Frank Tregear secured a seat in Parliament he sanctioned both marriages.
The social education of the Duke, begun by Lady Glencora, is continued by their children.