The following article contains mentions of child abuse and dissociative disorders.

Introduced in James McAvoy's most impressive movie roles, Kevin ends up shifting through numerous personalities and performances in the films.

Kevin's most dangerous personalities became present physical threats to the world around them. However, there's a deep bedrock of tragic trauma behind Kevin's origins that adds a somber edge to all of the fearsome elements carried out by his personalities in M. Night Shyamalan's Unbreakable trilogy. Here's the origin story of Split and Glass's Kevin Wendell Crumb, and how it set the stage for him to become the Beast.

Kevin Wendell Crumb's Origin & Childhood

Mr. Glass Killed Kevin Wendell Crumb's Father

Kevin Wendell Crumb's tragic history eventually led to his transformation into the Beast as part of the Eaststrail 177 trilogy. This transformed the nominally meek Kevin into a major antagonist in the latter two entries of the franchise. Kevin first appeared in Split and was partly inspired by Billy Milligan. Kevin was the child of Clarence and Penelope Crumb. When he was only three, Kevin's father "left" the family. It was later revealed this was because Kevin's father was onboard the fateful Eaststrail 177 and died when it crashed during the events of Unbreakable.

This makes Mr. Glass responsible for the death of Kevin's father, as he arranged for the train crash in the first place in a bid to find people with powers. Although this revealed his opposite in the super strong David Dunn, it also set up the circumstances that would birth the Beast. The trauma of this event played a part in worsening Penelope's DID, with at least one of her personalities lashing out at her son. The pain and neglect that Penelope put the young Kevin through resulted in him developing DID as well.

Kevin Wendell Crumb's DID & Personalities Explained

Kevin Wendell Crumb's Twenty-Four Personalities Were Often At War Over The Horde

By the events of Split, Kevin Wendell Crumb had developed twenty-four distinct personalities as a result of his DID. His condition also resulted in his body going through radical changes, with his body language and skills adjusting to whoever was in control of Kevin. Several of Kevin's personalities are among Split and Glass's characters, but some are absent from the plot. This includes Heinrich, Goddard, Bernice, Polly, Rakel, Felida, Ansel, Jalin, Kat, B.T., Samuel, and Ian. Others briefly appear, including the intellectual Orwell, the apologetic Norma, the Irish-coded Mary, stuffy film professor Mr. Pritchard, and the extroverted fashion designer Barry.

However, some of the personalities are shown to be far more fearsome and work to suppress the softer sides of Kevin. This includes the childish Hedwig, who can unleash different personalities. There's also the perverse Dennis and the domineering Patricia, with the trio forming the initial Horde. The Horde sees a personality known as the Beast as a purifying force and works to ensure his freedom in the world. The Horde only begins with three personalities but expands in Glass, with personalities like Jade and Luke ing their mission to free the Beast.

How Kevin Wendell Crumb Became The Beast

How Mr. Glass' Actions Led To Kevin Wendell Crumb Creating The Beast

The most dangerous of Kevin Crumb's personalities is the Beast, the final personality to develop. Born from Kevin's desire to have power over his life, the Beast is a vicious and powerful force that represents Kevin's trauma. The Beast has a particularly dark view of humanity, only willing to spare those who have suffered greatly in their lives and are therefore "pure" in his eyes. His appreciation for those who've endured trauma and pain is directly tied to the anguish that Mr. Glass caused by killing Kevin's father when he arranged for the crash of the Eaststrail 177 train.

The Beast possesses super strength, enhanced speed, and the ability to crawl on walls, and invulnerability. The only way to counter these powers is to force Kevin or one of the other personalities to take over, which can be forced with intense sudden lights or calling out to Kevin. This can trap the Beast in the powerless Kevin's mind, rendering him mortal. The end result of the abuse and neglect a young Kevin suffered in the backstory to Split, the Beast is perhaps the most iconic and frightening aspect of Kevin's DID and the direct result of Mr. Glass' plans.

Kevin Wendell Crumb Was Actually Inspired By A Real Person

Split Draws From The Real-Life Cast Of Billy Milligan

While Split is a fictional psychological thriller rooted in the mind of director M. Night Shyamalan, the character of Kevin Wendell Crumb and his 23 distinct personalities were loosely inspired by a real-life figure: Billy Milligan. Milligan became a media sensation in the late 1970s when he was arrested for the kidnapping and sexual assault of three women on the Ohio State University campus. During the investigation, psychiatrists diagnosed him with what was then called multiple personality disorder (now known as dissociative identity disorder, or DID), claiming he had as many as 24 different personalities inhabiting his mind. These included vastly different individuals ranging in age, gender, and even nationality.

Billy Milligan’s legal team successfully used his diagnosis to argue that he was not criminally responsible for the crimes, making him the first person in U.S. history to be acquitted of a major felony by reason of DID. Following the verdict, he was committed to a series of psychiatric hospitals for more than a decade. His case sparked nationwide debate, media coverage, and decades of fascination, including books and documentaries, eventually catching the attention of Hollywood creatives looking for complex, real-life psychological stories to adapt.

The parallels between Milligan and Kevin Wendell Crumb in Split are clear but intentionally dramatized. Both individuals are portrayed as having a multitude of distinct personalities, each with their own behaviors, speech patterns, and levels of awareness. Like Milligan’s alters, some of Kevin’s personalities in Split are benign or even helpful, while others (like Dennis, Patricia, and Hedwig) exhibit more dangerous or deceptive traits. The concept of certain alters "taking the light" in Kevin’s mind also mirrors how Milligan’s personalities reportedly rotated control of his body depending on external triggers and internal dynamics.

The idea that someone with DID is inherently dangerous or capable of extreme violence is not ed by clinical evidence. Individuals with DID are far more likely to be victims of abuse than perpetrators of it.

However, where Split veers sharply from reality is in the invention of “The Beast,” Kevin’s 24th and most terrifying identity, which possesses superhuman abilities, including wall-climbing, bullet resistance, and animalistic strength. There is no counterpart to this in the Milligan case, and the inclusion of a physically monstrous alter pushes Split into full-blown horror territory. Billy Milligan’s story, while deeply troubling and controversial, remained within the realm of mental illness, trauma, and the criminal justice system, whereas Split ultimately transforms Kevin into a supernatural antagonist, particularly as the film ties into the larger Unbreakable universe. Because of this, Split's depiction of DID walks a fine line between creative license and psychological misrepresentation.

While Shyamalan clearly drew inspiration from the real disorder and incorporated genuine aspects of how DID can manifest (such as memory blackouts, identity fragmentation, and distinct physiological traits between alters), critics and mental health professionals have been vocal in pointing out the film’s contribution to harmful stereotypes. The idea that someone with DID is inherently dangerous or capable of extreme violence is not ed by clinical evidence. Individuals with DID are far more likely to be victims of abuse than perpetrators of it.

By framing Kevin as a violent, nearly supernatural villain, Split reinforces stigmas that people with dissociative disorders have been working for decades to dismantle. That said, the movie also sparked renewed interest in understanding DID and prompted discussions about how trauma, especially childhood abuse - something both Milligan and Kevin suffered - can lead to the development of fragmented identities as a coping mechanism. Ultimately, while Split isn’t an accurate portrayal of DID, it succeeds in dramatizing the disorder in a way that blends horror and psychological intrigue, even if it sacrifices realism for spectacle.