Question: Who wrote an unofficial sequel-series of J.K. Rowling's Harry Potter universe, that enters around the character of James Sirius Potter who makes a fleeting appearance in the  final novel  of the "Harry Potter" series, written by British author J. K. Rowling?

Context articles: Religious debates over the Harry Potter series
Warner Bros. Entertainment Inc. v. RDR Books
Harry Potter in translation
Sam Clemmett
Harry Potter (film series)
Fantastic Beasts and Where to Find Them
The Magical Worlds of Harry Potter
James Potter (series)
Pottermore
Harry Potter and the Deathly Hallows

Religious debates over the "Harry Potter" series of books by J. K. Rowling are based on claims that the novels contain occult or Satanic subtexts.
 A number of Protestant, Catholic, and Orthodox Christians have argued against the series, as have some Shia and Sunni Muslims.
 Supporters of the series have said that the magic in "Harry Potter" bears little resemblance to occultism, being more in the vein of fairy tales such as "Cinderella" and "Snow White", or to the works of C. S. Lewis and J. R. R. Tolkien, both of whom are known for writing fantasy novels with Christian subtexts.
 Far from promoting a particular religion, some argue, the "Harry Potter" novels go out of their way to avoid discussing religion at all.
 However, the author of the series, J. K. Rowling, describes herself as a practising Christian, and many have noted the Christian references which she includes in the final novel "Harry Potter and the Deathly Hallows".
Warner Bros.
 Entertainment, Inc. and J. K. Rowling v. RDR Books, 575 F.Supp.2d 513 (SDNY 2008) is a copyright lawsuit brought on 31 October 2007 by the media company Warner Bros. and "Harry Potter" author J. K. Rowling against RDR Books, an independent publishing company based in Muskegon, Michigan.
 Lawyers for Rowling and Time Warner argued that RDR's attempt to publish for profit a print facsimile of "The Harry Potter Lexicon", a free online guide to the "Harry Potter" fictional universe, constituted an infringement of their copyright and was not protected by the affirmative defense of fair use.
 The trial was held from 14–17 April 2008 in the United States District Court for the Southern District of New York.
 In September 2008, the court ruled in Rowling's favor, and publication of the book was blocked.
 In 2009, RDR Books released an edited volume, eliminating the problematic long quotes found to be infringing.
The "Harry Potter" series of fantasy novels by J. K. Rowling have become some of the most widely read works of children's literature in history, with readers of all ages and in many countries.
 In April 2011 worldwide sales of Harry Potter books were estimated to be about 450 million copies.
 Oddly enough, it has been difficult to accurately determine with any degree of certainty exactly how many languages Harry Potter has been translated into.
 As best as can be determined (as of 2017), The Philosopher's Stone has been officially translated from the original English into 73 other languages.
 A 74th language, Scots, was announced on 2017-06-28 and it is expected to be available in October, 2017.
 Both Bloomsbury's and J.K. Rowling's sites have recently stated that the books have been translated into 79 languages (80 with the 2017-06-28 announcement of Scots); however, it has been argued that number actually represents the number of authorized translations (of The Philosopher's Stone) plus the original English.
 The number of authorized translations is not equal to the number of languages because there have been multiple authorized translations into the same language.
 Specifically, there have been two separate translations into each of: Mandarin Chinese, Portuguese, Romanian, Russian and Turkish (5 languages).
 English is often included in the list of translations even though technically it should not be (indeed, it is why our list here counts up to 74).
 Thus: 79 − English − 5 double-translations = 73.
 It is also worthwhile to emphasize that not all seven books are have been translated into these 73 languages.
Sam Clemmett is a British actor.
 Born in Brundall, Norfolk, Clemmett began his acting career in 2013.
 He is known for being cast as Albus Potter in 2015 for the British play Harry Potter and the Cursed Child.
 His performance in the play has made him popular with Harry Potter fans, as well as the creator of Harry Potter, J.K. Rowling.
 Rowling stated that, "There's much I could say about Sam-as-Albus, but we'd be into spoiler territory so quickly I'll just say we couldn't have cast better."
 He played the role in the West End, until late-Spring 2017.
Harry Potter is a British-American film series based on the "Harry Potter" novels by author J. K. Rowling.
 The series is distributed by Warner Bros. and consists of eight fantasy films, beginning with "Harry Potter and the Philosopher's Stone" (2001) and culminating with "Harry Potter and the Deathly Hallows – Part 2" (2011).
 A spin-off prequel series will consist of five films, starting with "Fantastic Beasts and Where to Find Them" (2016).
 The "Fantastic Beasts" films mark the beginning of a shared media franchise known as J. K. Rowling's Wizarding World.
Fantastic Beasts and Where to Find Them is a 2001 book written by British author J. K. Rowling (under the pen name of the fictitious author Newt Scamander) about the magical creatures in the "Harry Potter" universe.
 The original version purports to be Harry Potter's copy of the textbook of the same name mentioned in "Harry Potter and the Philosopher's Stone" (or "Harry Potter and the Sorcerer's Stone" in the US), the first novel of the "Harry Potter" series.
 It includes several notes inside it supposedly handwritten by Harry, Ron Weasley, and Hermione Granger, detailing their own experiences with some of the beasts described, and including in-jokes relating to the original series.
The Magical Worlds of Harry Potter: A Treasury of Myths, Legends, and Fascinating Facts is a guide to the fictional "Harry Potter" universe, written by David Colbert.
 It explores the references to history, legends, and literature in J.K. Rowling's "Harry Potter" novels.
 Colbert conceived the idea for "The Magical Worlds of Harry Potter" while quizzing his nephew and nieces about the mythological references in the novels.
 He later wrote the book while teaching a seminar on self-publishing to graduate students at the University of North Carolina.
 The book was published in March 2001, without approval from Rowling, and has since received positive reviews from critics.
 An updated version of "The Magical Worlds of Harry Potter" was published in 2004 by Berkley Books.
The James Potter series is an unofficial sequel-series of J.K. Rowling's Harry Potter universe, written by G. Norman Lippert.
 The novel series centers around the character of James Sirius Potter, Harry Potter's son, a character who makes a fleeting appearance in the novel "Harry Potter and the Deathly Hallows".
 The series starts with his first year at Hogwarts, set one year before the end of the Harry Potter series.
Pottermore is the digital publishing, e-commerce, entertainment and news company from J.K. Rowling and is a global digital publisher of Harry Potter and J. K. Rowling's Wizarding World.
 It offers news, features, and articles as well as new and previously unreleased writing by J.K. Rowling.
 The site features Rowling's thoughts, several pages of unpublished text, and a sales resource for e-book and audiobook versions of the seven "Harry Potter" novels.
Harry Potter and the Deathly Hallows is the seventh and final novel of the "Harry Potter" series, written by British author J. K. Rowling.
 The book was released on 21 July 2007, ten years after publication of "Harry Potter and the Philosopher's Stone" (1997), by Bloomsbury Publishing in the United Kingdom, in the United States by Scholastic, and in Canada by Raincoast Books, ending the series that began in 1997 with the publication of "Harry Potter and the Philosopher's Stone".
 The novel chronicles the events directly following "Harry Potter and the Half-Blood Prince" (2005), and the final confrontation between the wizards Harry Potter and Lord Voldemort, as well as revealing the previously concealed back story of several main characters.
 The title of the book refers to three mythical objects featured in the story, collectively known as the "Deathly Hallows"—an unbeatable wand, a stone to bring the dead to life, and a cloak of invisibility.