The Irony of Fleetwood Sr.'s Death
Casimir Fleetwood has enjoyed an uninterrupted relationship with his father for the majority of his childhood. His father's death is ironic because it occurs during Fleetwood's first trip away from home. As a welcome to adulthood, the death of one's father is a pretty severe, literal introduction.
The Irony of Mary's Pregnancy
Fleetwood believes that Mary is pregnant with Kenrick's child because of Gifford's lies. If, however, Fleetwood had bothered to fact check he would know that Mary had already been pregnant before the cousins arrived, so there is no possible way the child could be Kenrick's. He just didn't stop to challenge Gifford's deceptions.
The Irony of Marriage
Fleetwood marries Mary because he is attracted to her. He believes that she will bring joy and warmth into his life, which she does, but he is wrongly perceiving the function of marriage as well as Mary's own intentions. She doesn't marry him for love or attraction, but of necessity, having lost her family in a shipwreck. She needs him. For her, their union is practical, a disappointing revelation to Fleetwood.
The Irony of Fleetwood's Will
After learning his mistake, Fleetwood leaves his fortune to Mary and Kenrick and the baby. Having become the target of swindlers and thieves, Fleetwood no longer wants his estate, the one thing which made him attractive to everyone else. He never wanted the money, even though he had been raised in luxury. In fact, when he moves to the Pyrenees and lives on a very modest stipend, he achieves bliss. All along the inheritance had been his obstacle, a source of suffering, despite its seeming desirability to outsiders.
The Irony of Kenrick's Inheritance
Unlike his greedy brother, Kenrick comes to live with Fleetwood because he's curious. He's not seeking money or anything like that. In fact, he is honored by the opportunity just to live on such a nice estate. In the end, however, he is the one to inherit Fleetwood's fortune, despite his brother's many schemes to persuade Fleetwood to leave him the money. Since the brothers represent a natural dichotomy, their fates are ironic because the one who didn't seek wealthy found it, and the greedy one lost everything.
