Benito is Steven's brother and the eldest son of Felicia and Mr. Alacrán. He never really appears in the story, but we do hear about him from time to time, and we definitely don't like what we hear. Benito is yet another example of El Patrón's ability to mess with people's lives and make them miserable. Benito was forced to marry a Nigerian woman named Fani because El Patrón wanted an alliance with the powerful and rich Nigerian government. Benito can't stand Fani and the feeling is largely mutual. The two seem poised to become a lot like Benito's own parents, who have an extremely miserable marriage.
Eduardo and Lisa are the first two people we meet in the novel. They work in the cloning lab where they create Matt in a test tube. Eduardo and Lisa both seem stressed out over creating a clone, which gives us our first taste of just how dangerous and ruthless El Patrón is. The pair live in fear of being punished for failing. Eduardo in particular is scared for his family's safety. Eduardo also forms a special bond with Matt and worries about the child he's just helped to create.
Benito's wife is the daughter of the Nigerian president, and she was basically forced to marry into the Alacrán family for political reasons. Fani doesn't like her husband, and the feeling is definitely mutual. In the end, Fani suffers the same fate of the rest of the Alacráns and dies from drinking El Patrón's parting gift of poisoned wine.
Furball is María's small, fluffy, and extremely annoying dog. Tam Lin often threatens to do things to it, like suck it up in the vacuum cleaner. Senator Mendoza complains that the dog is obnoxious and smelly. Even Matt finds the dog horrible and spoiled. María babies the dog and won't let it out of her sight. Perhaps it's a way for María to cope with her mother's abandonment. In the end, poor Furball is poisoned by vengeful, Matt-hating Felicia.
Matt misplaces his resentment for being treated like an animal on this poor puppy, because he's the only animal around. Of course this isn't fair to the dog, but it's almost a form of self-preservation. Matt is angry, and it might be better that he take it out on the dog, instead of the powerful Alacráns, who are the real problem.
Guapo and Consuela are an elderly brother and sister pair. The two come to Matt and the Lost Boys' aid during their escape from the Keepers. After Conseula takes Matt and Fidelito to the Día de los Muertos festival to get them some much needed food, Guapo gives the two boys a ride to the hospital, where Chacho and Ton-Ton have already been delivered by an ambulance that the brother and sister had called.
Sister Inéz is one of the nurses at the Convent of Santa Clara hospital. She tends to Chacho and Matt as they recover from their ordeal in the boneyard. Sister Inéz also stands up to the Keepers when the men come to take Matt and his friends away.