Irony is defined in several ways. For instance, it is often described as the difference between what is said and what is meant, or the difference between what is expected to happen and what actually takes place. There are several kinds of irony: verbal, situational, dramatic, and rhetorical. Henry S. Leigh's poem "The Twins" is situational irony. As an example, situational irony is present...
...when a pickpocket gets his own pockets picked.
The crux of this poem's point is based upon the alleged confusion of identities with identical twins. The speaker bemoans the fact (with humor) that he has been confused with his brother his entire life. It began (he jokes...for how could he possibly know any such thing) with his nursemaid:
One day, to make the matter worse,
Before our names were fixed,
As we were being washed by nurse,
We got completely mixed...
In is not just that the two are mistaken for each other: the speaker says his brother took his entire life. The poet relates various instances where confusion ruled his life: he got whipped ("flogged") for his brother's misbehavior ("For John turned out a fool"); he even started to date a woman who became his brother's wife! He has continually asked all he knew:
What would you do, if you were me,
To prove that you were you?
But if John was his brother, and the speaker was Henry, then how could the two be confused? They were who they were.
The speaker recounts how this confusion continued throughout his life until he (the speaker) "died."
In fact, year after year the same
Absurd mistakes went on,
And when I died, the neighbors came
And buried brother John.
However, in that everyone had always confused the two, he relates that the same situation existed at this point, for while he felt his brother had had his identity and lived his life, when it was time to die, his brother took his place in that as well. Ironically, if John took the speaker's identity since his birth, it is logical that he should also take the speaker's death. And this is where the humor lies...for John was always John. Technically, the only thing that could have been confused was a name, which would have had no bearing (we can assume) on the behavior, choices or fate of either boy.