"Take it easy, kid," he says, pressing down on my chest to calm me. "I've got you." (1.15)
The language Denny uses here to describe Enzo, emphasizes how much he thinks of Enzo as not only a part of his family, but as a child. Denny, more than anyone else, raised Enzo. He's Denny's doggy son.
The life that Eve had inside her was something she had made, She and Denny had made it together. I wished, at the time, that the baby would look like me. (6.9)
By saying that he wishes that the baby looked more like him, Enzo reveals his wish to integrate himself into the family better, to connect to the family that Denny and Eve are building together—and that Enzo might fear they are building without him.
Soon after [Eve] moved into our apartment, they were married in a small wedding ceremony, which I attended along with a group of their closest friends and Eve's immediate family. (6.3)
Denny's idea of family is something small and close-knit. There are some complicated reasons for Denny's thinking—his idea of family is certainly different from Eve's—but is there one right definition of family?
It was loud and crazy and all the children let me play with them and wrestle on the rug, and I let them dress me up with a hat and a sweat jacket and Zoë called me her big brother. (7.19)
The turning point here is that Zoë, the cause of Enzo's initial worry that he might never be loved as much as the unborn child, already loves Enzo so much that it's clear he never even needed to worry about anything in the first place. Enzo probably makes a fantastic big brother.
And while I greatly resented the attention Eve lavished on her unborn baby, I realized I had never given her a reason to lavish that same attention on me. Perhaps that is my regret: I loved how she was when she was pregnant, and yet I knew I could never be the source of her affection in that way because I could never be her child. (6.6)
Enzo desires to connect to Eve as she connects to her unborn baby. Well, okay, but unless he can figure out how to reverse-engineer the miracle of life, he's going to have to be content with being her pet.
But many others were, all of whom were relatives of some kind or another. We were only there, I overheard, because Eve had thought it was very important for Zoë to spend time with these people, since she, Eve, someone said, would die very soon. (25.1)
Zoë doesn't seem to have any connection to these people, but because of social conventions and blood relations, she's mandated to at least meet them before her mother dies. Sure, if that's necessary. But does that really make them family?
I could see that Denny was stuck. He had agreed to have Eve stay with Maxwell and Trish, and now they wanted Zoë, too. If he objected, he would be keeping a mother and a daughter apart. If he accepted their proposal, he would be pushed to the periphery; he would become an outsider in his own family. (23.45)
Just as Denny's conception of family is small, so is Maxwell and Trish's, and we've seen time and again that they don't believe he has a place in what they consider their family. As we've said before, it's because they're jerks.
The barking of coyotes, my brethren, calling each other to the hunt. (25.4)
Even though Enzo knows he is part of the Swift family, he also acknowledges that the he is still a canine, and as such, he is related to the wilder animals of the night and the forest.
Always pushing the extremes. Finding himself broke. And finding himself on the telephone with his blind mother, asking her for some kind of help, any kind of help, so that he could keep his daughter; and her response that she would give him everything if only she could meet her grandchild. (55.3)
Sometimes families are estranged: just look at Denny and his parents, for example. But real family, the family that is dependable and steadfast despite differences and time, will drop everything to help if they're able. Where his parents were when Denny stubbed his toe that one time, we'll never know, but they pulled through in the end.
I can hear Denny in the kitchen. I can smell what he's doing; he's cooking breakfast, something he used to all the time when we were a family, when Eve was with us and Zoë. For a long time they have been gone, and Denny has eaten cereal. (58.2)
Just as family can give you everything you ever needed or wanted, the absence of family can also take everything away from you and leave you without the will to take care of yourself or even muster up enough strength to care about anything. Or maybe Denny's just been reverting to bachelor status?