She built an entirely new world of characters and places in the Harry Potter novels, but author J.K. Rowling will learn something about her own history during the premiere of Who Do You Think You Are? on Aug. 2. 

The British writer, 49, explores a handful of her ancestors in the sneak peek from the upcoming season of the TLC investigative series. In the episode, Rowling travels to France to trace her mother’s side of the family.

Rowling’s mom tragically died before the author had the chance to publish her first Harry Potter book. 

“Oh my God, he killed several German soldiers,” the shocked writer says after uncovering military records for one of her relatives. 

She also learns that her 2x great-grandmother was a struggling single mother (as Rowling was pre-Potter) who was “a witness to German invasion during wartime, which forced her family to choose sides in a time of turmoil,” the release reads. 

“I feel that we are what we are really because of her bravery,” Rowling says in the clip. 

Watch it now to see what she discovers! J.K. Rowling’s episode of Who do You Think You Are? airs Sunday, Aug. 2, at 9 p.m. ET on TLC. 

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