Final answer:
In 'The Adventures of Huckleberry Finn' by Mark Twain, it is Huckleberry Finn who bitterly weeps when a slave family is sold off by the King and Duke, highlighting the cruelties of slavery and Huck's developing moral compass.
Step-by-step explanation:
The character who bitterly wept when a slave family was sold off by the King and Duke is Huckleberry Finn, from the novel 'The Adventures of Huckleberry Finn' by Mark Twain. This scenario demonstrates the emotional impact of the inhuman practice of slave trading on individuals who are empathetic to the sufferings of the slaves and serves as a poignant critique of the institution of slavery.
Huck's response to the situation reveals his growing moral conscience and stands in stark contrast to the callousness of the swindlers, the King and Duke, who treat the sale of human beings as a means of profit.