Role in the film
Alberto and Antonio are first seen at the L.A.P.D. K-9 training facility approaching Delgado and Chloe. Alberto asks: "What are you doing here?" and just when Delgado tries to talk to them, Antonio states that they're busy working on a bank robbery case. When Chloe assures them that they can rely on her and Delgado to help them out, Antonio replies: "Not if one of them happens to be your father. He's never had our back.", thus, revealing to Chloe that Alberto and Antonio are actually Delgado's sons. Then, one of the cops whistles for Alberto and Antonio to join them while saying good-bye to them. Delgado thought that with Chloe by his side he would have the courage to tell them the truth about why he had abandoned them as puppies at the L.A. police station in the first place.
In a flashback while telling Chloe and Papi the story, it is revealed that the reason why Delgado abandoned his sons as pups was because three years ago when he was still on the Mexican police force, he and his team of cops apprehended some really bad guys and their dogs. Those dogs said they would get their revenge by hurting his pups, so, he took them in a basket far away to L.A. and left them at the doorstep of a police station while ringing the bell; thinking they would be safer away from him. So, his sons grew up to be fine K-9 officers. Nevertheless, it was the hardest he had ever done and he had lost contact with his sons ever since until recently. Try as he might to tell them the truth, Delgado states that "his sons won't listen (thinking their father abandoned them for no reason) and after the dog show, he's going back to Mexico"; probably never to see his sons ever again.
The next day, a bank robbery occurs and the cops intend to handle the situation while bringing Alberto and Antonio along with them in a truck. In the truck, Alberto and Antonio find 5 Chihuahua puppies: Papi Jr., Pep, Ali, Rosa, and Lala (Papi and Chloe's pups actually) climbing aboard. Alberto states that the truck is police property but Papi Jr. replies that he and his sisters are friends of their father and are here to tell them the truth. Once they arrive at the crime scene, Alberto and Antonio get out to do their job; not before Alberto tells them to stay put and that they'll discuss everything later on.
A few moments later, after the bank robbers had given the cops the slip, Delgado approaches his sons with a ski mask, which one of the robbers had unintentionally left behind and which might lead them to Chloe's pups who were unnoticeably taken by the robbers, and with Chloe by his side to help them with their investigation. Alberto and Antonio wonder what he's doing here and Delgado asks them to help him with the missing pups and that the mask might help lead them to them. Antonio smells ingredients from the mask: Flour, eggs, and butter and Alberto concludes it's bread, thus, meaning the criminals' hideout must be at a bakery factory. While Chloe, Papi, Delgado, and Pedro go after the pups at the Hoffman Bakery factory, Alberto and Antonio say they will "grab the humans and meet them there."
After Chloe, her family, and her friends catch the crooks, Alberto and Antonio are seen leaving with the cops; not before approaching their father, apologizing to him, and thanking him for what he had done after finding out the truth from Chloe and the pups. Delgado admits he's just glad he had a chance to see them again and to make things right. When a cop, impressed by Delgado's bravery and sense of smell and tracking, approaches him, he finds his collar belonging to the Mexican police force, stating he and the other cops could "use his nose on a couple of cases" and when he asks Alberto and Antonio about what they think, they bark altogether in agreement. So, the cop gets their hint and goes to give the Mexican police force a call. Delgado asks his sons if they really want him to stay and they reply that they all have a lot of catching up to do and that it's great to have their father back. Finally, Alberto and Antonio are last seen entering the truck with their father.