Thomas and I are identical twins, not fraternal—one fertilized egg that split in half and went off in two directions. (1.8)
Two directions is putting it mildly. One brother ended up with anger management problems and the other ended up with severe mental illness. They might look the same, but they are wildly different on the inside, like one Twinkie filled with vanilla and another filled with banana crème.
I loved my brother. I hated him. There was no solution to who he was. No getting back who he had been. (1.36)
Dominick loves the Thomas he remembers, but he hates the person Thomas has become. It's like he's a different person entirely.
Take it from the uncrazy twin—the guy who beat the biochemical rap. (3.1)
Dominick always defines himself in relation to Thomas. We'll see this a lot during the book. But we'd just like to make a minor correction here, and call Dominick the differently crazy twin. He's not exactly uncrazy, he's just nuts in a totally different way.
"That's what's a little scary. Sometimes he seems like some weird version of you." (6.120)
Dominick worries about being confused with Thomas. He doesn't want to be identified as Thomas's brother, much less being identified as Thomas himself. It's like Jerry meeting bizarro Jerry, but not funny.
"It frightens you, doesn't it, Dominick: the thought that you, too, could become mentally ill?" (17.281)
This is part of the core of Dominick's fear and frustration, and it recalls the quote about twins being one fertilized egg that goes in two different directions. What if the mental illness didn't entirely pack up and go with Thomas? What if it's part of Dominick's identity, too?
"You are me," he said. […]
"No, I'm not," I said. "Far from it."
"Yes, you are." (21.105-21.110)
This is an exchange between Thomas and Dominick. What do you think Thomas means here? That Dominick is "crazy," too? Or that they're two halves of the same coin? Some sort of clone? What?
[Thomas] burst into tears. "Because I'm dirt. Because I'm nothing but a greedy little pig." (26.95)
This is a sad quote that shows how being bullied and beaten can change someone's sense of self into thinking they deserve the horrible treatment they're subjected to.
I was no longer simply Domenico Tempesta—I was both myself and a crazy man! (37.101)
We'd argue that Domenico is a crazy man, but what's really relevant here is how Domenico has the personalities of Thomas and Dominick rolled up into one person—he's a crazy man with anger issues. A charming combo.
It's over, I thought; now he knows: I'm the bad twin. I'm the troublemaker. Not Thomas. Me. (42.64)
What is this, a soap opera? We wish Dominick would get over this whole bad twin/good twin dynamic. It's not always that black and white. A person's identity is composed of many shades of gray, and in his refusal to see that, he short-changes himself and his brother.
We 415 members of the Wequonnoc Nation are millionaires. (48.5)
Notice that Dominick says we here. He's known that he's Wequonnoc Indian for about five seconds, and he already identifies himself as one of the tribe.