The irony of little Gus
When the father does something, usually it's Gus who emulates him most clearly. If the father drops something, Gus will pick it up. He realizes early on that by being on the side of the father, he can enjoy a little more attention than the rest, but even that becomes dysfunctional because he decides to steal his father's own wallet and then return it to him for praise. The stunt is ineffective.
The ironic affair
When the morally decent wife decides to have an affair, it might seem out of character, but one must remember that people have a need for romantic attention, and since the husband has permanently cut himself off from the family, emotionally speaking, she is left lonely and tempted. In an additional ironic twist, she picks a man who already has a couple of girlfriends.
The confusing death
When Rosie is found dead, Sherman suspects that it was suicide. This ironic event is so sudden that the idea of it happening by chance doesn't even seem possible to Sherman.
The remarriage
The father remarries after the death of his wife. This might seem ironic, given how much he hated being married, and given the trauma of losing one's wife, but there might be the insinuation that perhaps he has dependence issues.
The ironic unity
The novel ends with an image of the family reunited once more to honor the mother. He scatters the ashes, and the family shares a strange moment together, united and intimate, but also sad and deeply confused about life. The unity stands in contrast to the family's tendency toward dysfunction.
