The Harry Potter fan theory that reveals the Dursleys aren't as terrible as you thought.

If you’re a Harry Potter fan, you’ll probably remember the deep resentment you held towards the Dursleys.

You know, the terrible, ignorant, cowardly family who would do just about anything to avoid anything out of the ordinary – including locking their nephew, boy-wizard Harry Potter in the cupboard under the stairs.

If you need a little refresher, Harry Potter was brought up by his mother’s sister, Aunt Petunia and her husband, Uncle Vernon after his parents Lily and James Potter were murdered by Voldemort.

The Dursleys, including their son Dudley, openly resented Harry, banishing him to a lonely childhood in the cupboard under the stairs while Dudley was spoiled with attention and piles upon piles of food and presents.

But now, over 20 years since the record-breaking first Harry Potter book was released, fans have uncovered a theory which may suggest why the Dursley family were so damn awful.

Watch: It’s been 20 years since the first Harry Potter book.

Although some believe that the Dursley family were simply terrible people who believed in nothing more than social status and money, according to The Mirrora fan theory suggests that there was actually a magical reason behind their hatred of Harry.

And it all comes down to Horcruxes.

Throughout the book and film series, characters who got too close to Horcruxes (objects containing parts of dark wizard Voldemort’s soul) were affected by them.

In the second film, Harry Potter and the Chamber of Secrets, for example, Ron Weasley’s younger sister Ginny is possessed by one of the Horcruxes – Tom Riddle’s diary.

As it later turned out that Harry himself was one of Voldemort’s Horcruxes, the theory suggests that Harry himself may have been influencing the Dursley family’s terrible behaviour.

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Harry Potter and Ginny Weasley in Harry Potter and the Chamber of Secrets. Image: Warner Bros.

Maybe the Dursleys weren't as bad as we thought?

In 2015, J.K. Rowling shared further details behind why Vernon and Petunia hated Harry.

Rowling said that Vernon's hatred for Harry stemmed from his hatred of Harry's father James, who Vernon despised.

On the other hand, Aunt Lily was jealous of her sister Lily, but deep down she loved her. She tolerated Harry and kept him around simply because she was afraid she would never see her sister's eyes again.

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Uncle Vernon, Dudley and Aunt Petunia. Image: Pottermore.

In J.K. Rowling's new play, Harry Potter and the Cursed Child, Harry's relationship with the Dursleys seems to be doing much better.

In the play, Harry shows his son Albus his baby blanket, which Petunia had keep hidden away over the years.

"Dudley found this and he kindly sent it to me," Harry says – an indication that perhaps Aunt Petunia wasn't as evil as we originally thought.