HUNTINGTON PARK, Calif. – Many of the Castro family’s photos feature the same muscly dog. Their family pet, Kimbo, attended the graduation of breeder Gustavo Castro’s eldest daughter and cuddled with his young daughters on their couch.

But Kimbo also graced the pages of newspapers when the Castro family found their pet at the center of a contentious fight to ban its breed — the American XL Bully — throughout the United Kingdom.

Since early 2023, XL Bullies have been named as the perpetrators in a slew of recent attacks. Victims include a boy as young as 10 named Jack Lis, whose mother, Emma Whitfield, called the breed a “clear and lethal danger to our communities, particularly to children.”

Government data showed a marked increase in the number of fatal attacks in 2023, though this data is not broken down by breed. Under pressure from anti-Bully campaigners, the government announced a ban on “XL Bully type dogs,” adding the breed to the list of dogs that fall under the Dangerous Dogs Act.

Both Castro and the self-proclaimed creator of the breed, Dave Wilson, spoke out against the addition of the XL Bully to the act, which makes breeding or selling a dog resembling the breed illegal. Any owners already in possession of an XL Bully must register and neuter their dog, only taking it out in public on a leash and with a muzzle.

“The decision to ban XL Bully dogs was made following a concerning rise in attacks from these dangerous dogs, with 23 people sadly losing their lives after vicious dog attacks in the last three years,” a government post reads. “XL Bullies have been involved in many of these tragic deaths.”

Kimbo with one of Gustavo Castro's daughters.

Castro — a breeder and father who maintains pride in the prolificacy of his dogs, all while in the face of the death and injury attached to his and Kimbo’s name — said that he has never been bitten.

And Wilson, who said he bred his bullies to be docile, argued that the government may be getting it all wrong. And despite Castro saying otherwise, Wilson said that Kimbo — nicknamed the United Kennel Club registry’s “most wanted” — might not even be what has come to be known as the XL Bully.

The Castro family reacts to ‘Killer’ Kimbo’s new legacy

Amid discourse surrounding the ban, Kimbo emerged as a figurehead of the threat posed by the XL Bully after an advocacy group called Bully Watch U.K. published the results of an investigation into the responsible pedigrees for the attacks.

Bully Watch U.K. wrote that their investigation — titled 'Finding Kimbo' — led them to repeatedly unearth one name: “It was a name that has gained infamy in the United States. A name that left us speechless and sent a cold shiver down our spines. One we never expected to uncover.”

According to Bully Watch U.K., approximately half of the XL Bully population throughout the U.K. can be traced back to Kimbo. The organization also said their research showed that Kimbo’s gene pool is responsible for 70 percent of dog attacks in Britain, a finding that catapulted Kimbo’s name into headlines.

“I was sad, I was mad,” Castro said about seeing his dog’s name pop up in the press. “There’s a lot of people that hate them, but then there’s people that love them a lot,” he said of the breed.

Castro said this love keeps him going, as, despite the distance between Southern California and the U.K., the discourse involving him and his dog, who died around a decade ago, impacts him deeply. It’s “basically my blood,” he said.

While Gustavo Castro’s daughter Valerie Castro said her father was no longer a constant in her life, Kimbo always was. When she saw Kimbo linked to death and injury throughout the U.K., Valerie Castro said her family laughed.

Bullies “are the most loving and caring animals that there are, so it’s just ridiculous to me how some people think otherwise,” Valerie Castro said. She added that her family has never experienced behavioral issues with their dogs.

Growing up, Valerie Castro and her five sisters acted as “models” for their father, posing with the dogs in what she called an effort to “cut the stereotype” that they are aggressive. Gustavo Castro left the family home in recent years, Valerie Castro said, but left some dogs behind. They were raised and kept in good health by her sisters, she said.

Valerie Castro said that as the oldest, she still keeps in touch with her father. “He moves around a lot,” she said, adding that she is used to co-parenting her younger sisters with her mom. But memories of helping her father with his dogs are good ones, she said.

“His work was never an issue,” Valerie Castro said, remembering the dogs as “friends.” While Kimbo was bred, a process that had to be timed carefully, especially when a client lived overseas, he was always more of a family pet, she recalled. “He was never something to make money off of.”

What is an XL Bully, according to the breed's creator?

Some experts present at a meeting of the Environment, Food and Rural Affairs Committee in Oct. 2023 said that no breed of dog is inherently aggressive, but in the case that a dog is aggressive, a larger, more powerful one will cause more damage. And with an estimated 50,000 XL Bullies living throughout the U.K., concerns about the muscular dogs prevailed.

But while the dogs look aggressive, Wilson, the breed’s creator, said his original intention was to try and fight against the stigma normally associated with dogs that look like Pitbulls by creating one with a docile temperament. Wilson’s breed — the American Bully — looks “like a bodybuilder,” but is “very mellow,” he said.

American Bully breeders at a dog show in Visalia, California react to the ban overseas.

In the early 2000s, when Wilson created the American Bully breed, he decided to start his own registry called the American Bully Kennel Club. All of the original dogs entered into this registry would be the foundation of the breed, meaning any American Bully should be able to trace its lineage back to the club’s first studs.

“This breed has grown like no other breed around the world,” Wilson said. “Up until recently, we’ve never even had anything negative towards our breed.”

The breed appears on the Dangerous Dogs Act as XL Bully “type” dogs, but Wilson said this label is misleading. The breed is better known as the American Bully, and the “XL” is one of three size classifications within the breed, Wilson explained.

An American Bully can be either of the pocket, standard or XL variety, Wilson explained. But only the XLs are taking any heat, he said. The negative connotations surrounding the dogs caught Wilson off guard, he said, as there is no difference save for height between the breed’s three varieties.

Wilson said he’s concerned that the new laws don’t provide clear guidance on how to properly identify the dogs and worries identification issues began before the law came into effect.

Of the more than 90,000 dogs in his registry throughout the U.K., Wilson said none have been involved in any of the attacks. “They have no actual documented cases of what they say is an XL American Bully biting a person,” Wilson said.

There’s one name also missing from Wilson’s database: Kimbo, who is registered with the United Kennel Club. According to Wilson, Kimbo was registered with the club before it started recognizing the American Bully breed. According to an entry in Bullypedia, a database of dog pedigrees, Kimbo is listed as an American Pitbull Terrier. Castro, however, said Kimbo is an XL Bully.

Wilson said he doesn’t trust Bully Watch U.K.’s information, which carries a disclaimer that reads, “We want to be completely transparent with our research. It’s not perfect. It is back of napkin. But we think it fills a gap in the literature.” The site does not identify who is behind the campaign.

The clock strikes midnight for dogs and their owners

As the country prepared to ring in the new year on Dec. 31, 2023, the XL Bully ban came into effect.

The dogs had been officially added to the Dangerous Dogs Act two months prior, giving owners time to prepare for the first stage of the ban. On New Year's Eve, it became illegal to breed, sell or exchange the dogs. All dogs had to be registered and exempted by Feb. 1, and any dog older than one had to be neutered starting at the end of June.

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Any owner who wished to put their dog down could receive £200 in compensation by filing a claim alongside a vet regarding the euthanization, according to the government's website.

Maxwell Connor, an XL Bully owner in the U.K. whose dogs descend from Kimbo, called the period “a horrible time.”

Connor said he was working on raising thousands of pounds to apply for exemptions for his dogs and get them neutered as the deadlines neared. “If I’m honest, I’m scared every day I get closer,” Connor said. “I put my all into mine.”

Mourning the dozens who lost their lives in attacks, Bully Watch U.K. said in a post on X that the ban is a step in the right direction. “We must go further and completely reform our approach to dog regulation and ownership in the UK,” the organization said.