The Stolen Heir duology is set in the same world as The Folk of the Air series. The Folk of the Air trilogy includes The Cruel Prince (2018), The Wicked King (2019), and The Queen of Nothing (2019)—which feature the eventual High King Cardan and High Queen Jude. How the King of Elfhame Learned to Hate Stories (2020) is a companion novella to the trilogy. The Stolen Heir takes place eight years after the Battle of the Serpent, a major conflict in The Queen of Nothing.

The Cruel Prince introduces Oak’s family. His parental figures are Madoc, a ruthless redcap faerie who dips his cap in the blood of his enemies, and Madoc’s second wife, a faerie named Oriana. Together, the couple raises four children: Vivienne, the eldest, the part fae, part human daughter of Madoc and his first wife, a human woman named Eva; Taryn and Jude, human twins born to Eva and her human husband, Justin, after she fled to the mortal realm; and Oak, the youngest, who is widely regarded as Oriana’s biological child.

Oak is a child in The Cruel Prince, raised by Madoc and Oriana—but as events unfold, it is revealed that he’s the secret child of Dain, heir to the High King of Elfhame, and Liriope, a consort to the current ruling King of Faerie.