The Farnsworth Empire that has been established hundreds of years ago was founded by the first King; Edward Hawthorne assisted by his three confidants who were given the title of Duke namely from the family: Bridget, Hildegard and Lorelei. The three families have always held their oath to the Hawthorne family which is the Imperial family of Farnsworth.
The current Emperor, Brixton Eren Hawthorne planned to strengthen his power as he was the son of a concubine not an empress. He cunningly overthrew the throne of his elder brother who was the rightful heir (son of the Emperor and Empress) imprisoned him on charges of selling imperial information and then executed him with several nobles who he thought would disturb him.
Although he is now sitting on the throne, he remains fiercely insecure as the Empress is still alive and may hold a grudge. As much as he wanted to get rid of her, Brixton could not have his name written in history as the tyrant who killed the Empress Dowager.
But he had a way of weakening the Empress Dowager's power by marrying the daughter of a high noble who would become his ally.
The Bridget family became the choice because of their hundreds of years of loyalty to the ruler. With the news that Bridget's daughter was of marriageable age, Brixton would make her his strongest ally, his big weapon for the fall of the Empress Dowager.