What crime does Ike accuse his grandfather or committing, and what proof does he have of this crime?

While reading through the old ledgers, Ike is disgusted to learn that his grandfather often had "favorite" slaves, females that he would engage in sexual relationship with, either forcibly or amicably. Ike is further disturbed to learn that his grandfather fathered a child with one of his favorite slaves, Eunice, a daughter that was named Tomasina. Through reading the ledgers further, Ike learns that his grandfather fathered another child with his own daughter, which means that his grandfather was guilty of incest, a fact that makes Ike shudder.