Question: Who are the parents of the goddess the title of the final novel of the "Percy Jackson & the Olympians" series refers to?

Context articles: The Demigod Files
The Sea of Monsters
Hestia
Percy Jackson: Sea of Monsters
The Titan's Curse
Camp Half-Blood chronicles
The Last Olympian
Percy Jackson
The Lightning Thief
The Battle of the Labyrinth

The Demigod Files is a collection of stories by Rick Riordan published on February 10, 2009.
 It is a companion book to series "Percy Jackson & the Olympians".
 It contains three short stories, titled "Percy Jackson and the Stolen Chariot", "Percy Jackson and the Bronze Dragon", and "Percy Jackson and the Sword of Hades", as well as a preview of "The Last Olympian".
 It is set between the fourth and fifth novels, "The Battle of the Labyrinth" and "The Last Olympian".
The Sea of Monsters is a fantasy-adventure novel based on Greek mythology written by Rick Riordan and published in 2006.
 It is the second novel in the "Percy Jackson & the Olympians" series and the sequel to "The Lightning Thief".
 This book chronicles the adventures of thirteen-year-old demigod Percy Jackson as he and his friends rescue his satyr friend Grover from the Cyclops Polyphemus and save the camp from a Titan's attack by bringing the Golden Fleece to cure Thalia's poisoned pine tree.
In Ancient Greek religion, Hestia ( ; Greek: Ἑστία , "hearth" or "fireside") is a virgin goddess of the hearth, architecture, and the right ordering of domesticity, the family, the home, and the state.
 In Greek mythology, she is a daughter of Cronus and Rhea.
Percy Jackson: Sea of Monsters (also known as Percy Jackson & the Olympians: The Sea of Monsters) is a 2013 American fantasy adventure film directed by Thor Freudenthal.
 It is the second installment in the "Percy Jackson" film series and is loosely based on the novel "The Sea of Monsters" by Rick Riordan.
 It is a stand-alone sequel to the 2010 film "".
The Titan's Curse is a 2007 fantasy-adventure novel based on Greek mythology written by Rick Riordan.
 It is the third novel in the "Percy Jackson & the Olympians" series and the sequel to "The Sea of Monsters".
 It charts the adventures of the fourteen-year-old demigod Percy Jackson as he and his friends go on a dangerous quest to rescue his friend Annabeth Chase and the Greek goddess Artemis, who have both been kidnapped.
Camp Half-Blood Chronicles is a media franchise created by author Rick Riordan, encompassing three five-part novel series, three short-story collections, two myth anthology books, a stand-alone short story, an essay collection, a guide, four graphic novels, two films, a video game, a musical, and other media.
 Set in the modern world, it focuses on groups of demi-god teenagers, and features many characters from Greek and Roman mythology.
 The first series, "Percy Jackson & the Olympians", follows the adventures of a teen named Percy Jackson at a summer camp for Greek demigods.
 The second series, "The Heroes of Olympus", introduces several more lead characters and a second camp for Roman demigods.
 The third series, "The Trials of Apollo", follows the now-mortal god Apollo, with appearances by many characters from the first and second series.
The Last Olympian is a fantasy-adventure novel based on Greek mythology by Rick Riordan, published on May 5, 2009.
 It is the fifth and final novel of the "Percy Jackson & the Olympians" series and serves as the direct sequel to "The Battle of the Labyrinth".
 "The Last Olympian" revolves around the demigod Percy Jackson as he leads his friends in a last stand to protect Mount Olympus.
 The title refers to Hestia, the goddess of the hearth, who refers to herself as such in a conversation with Percy on Mount Olympus.
Perseus "Percy" Jackson is a fictional character, the title character and narrator of Rick Riordan's "Percy Jackson & the Olympians" series.
 He is also one of seven main protagonists of the sequel series "The Heroes of Olympus", appearing in every book except "The Lost Hero," and appears in the ongoing "Trials of Apollo" series, making him one of the few characters to appear in all three series of the Camp Half-Blood chronicles.
 He has also been a narrator and protagonist in Riordan's Greco-Roman/Egyptian crossover stories, part of the "Demigods and Magicians" collection.
 The character serves as the narrator in "Percy Jackson's Greek Gods" and "Percy Jackson's Greek Heroes", also by Rick Riordan.
The Lightning Thief is a 2005 fantasy-adventure novel based on Greek mythology, the first young adult novel written by American author Rick Riordan.
 It is the first novel in the "Percy Jackson & the Olympians" series, which charts the adventures of modern-day twelve-year-old Percy Jackson as he discovers he is a demigod, the son of a mortal woman and the Greek god Poseidon.
 Percy and his friends Annabeth Chase and Grover Underwood go on a quest to prevent a war between the gods Zeus, Poseidon, and Hades.
The Battle of the Labyrinth is a 2008 fantasy-adventure novel based on Greek mythology; it is the fourth novel in the "Percy Jackson & the Olympians" series by Rick Riordan.
 Percy Jackson, a fictional demigod (who is fifteen years old by the end of the book) attempts to stop Luke Castellan and his army from invading Camp Half-Blood through Daedalus's labyrinth by trying to convince the inventor not to give Ariadne's string to Luke.