Warning: This post contains spoilers for Dune: Part Two.

When Jessica (Rebecca Ferguson) makes the decision to ingest the Water of Life and undergo the ritual of Spice Agony in order to become the Fremen’s new Reverend Mother in Dune: Part Two, now in theaters, she expects to unlock the memories of all of her female ancestors. What she doesn’t anticipate is learning her father is someone she never suspected: the Baron Vladimir Harkonnen (Stellan Skarsgård).

Paul (Timothée Chalamet), who ends up drinking the Water of Life later in the film, eventually also becomes privy to this information and confronts his mother about it. Director Denis Villeneuve opts not to delve too much into the backstory behind the reveal, but it shouldn’t come as a surprise to those who have read the Dune books.

Frank Herbert’s classic 1965 novel lets readers in on the secret of Jessica’s parentage a little earlier in the story, shortly after Paul and Jessica have escaped into the Arrakis desert in the wake of the Harkonnen and Sardaukar assault on House Atreides. Paul’s younger sister, Alia Atreides, then learns the identity of her grandfather when she is pre-born in Jessica’s womb and, in the book, goes on to kill the Baron. In the movie, Paul is the one to kill him instead.

Read more: How the Ending of Dune: Part Two Sets Up a Third Movie

In the third Dune novel, Children of Dune, Herbert notes that Jessica’s mother was a Bene Gesserit woman named Tanidia Nerus. However, in the Prelude to Dune prequel trilogy written by Herbert’s son Brian Herbert and Kevin J. Anderson after the author passed away, it’s revealed that Tanidia Nerus was the birth name of Reverend Mother Gaius Helen Mohiam (played in the movies by Charlotte Rampling).

While Brian Herbert and Anderson have said this information was pulled directly from Frank Herbert’s working notes for the original Dune series, there is some disagreement among fans about what is actually canon. For the purposes of the illustration below, we’ve stuck to only what’s included in Frank Herbert’s published work. We’ve also left Princess Irulan’s (Florence Pugh) four younger sisters out of the graphic, as they don’t play a role in the Dune movies.

See TIME’s Dune family tree below.

Read more about Dune:

• Denis Villeneuve explains making Dune: Part Two
• How a surprise character arc shakes up Dune: Part Two
• Why filmmakers have struggled to adapt the books