Back To The Future's McFly Family Tree Across All 4 Time Periods Explained
Richard Craig is a Senior Author at Screen Rant covering film and TV. Richard has also written extensively about horror and film soundtracks, contributing a chapter to the first major academic collection on the folk horror genre, The Routledge Companion to Folk Horror. Richard is also a performing musician and holds an MA in Music and Sound Art.
The complete McFly family lineage across Back to the Future's four major time periods is surprisingly extensive. Across Back to the Future (1985), Back to the Future Part II (1989), and Back to the Future Part III (1990), Marty McFly's adventures take him to 1885, 1955, 1985, and 2015. While the trilogy is primarily remembered for its time-travel mechanics, the movies also spend a remarkable amount of time exploring Marty's family history.
The McFlys become a way for Back to the Future to show how personality traits, family relationships, and even recurring conflicts can echo across generations. One of the trilogy's running jokes is that every Back to the Future timeline seems to contain both a McFly and a Tannen. Whether it's George being bullied by Biff in 1955, Marty dealing with Biff's descendants in the future, or Seamus McFly crossing paths with Buford "Mad Dog" Tannen in the Old West, the families remain connected throughout history.
The films also use casting to reinforce these connections. Michael J. Fox plays multiple members of the McFly family, while Lea Thompson portrays both Lorraine Baines McFly and Marty's great-great-grandmother. The result is a family tree that stretches from nineteenth-century Irish immigrants to Marty's own children living in the futuristic version of 2015 seen in Back to the Future Part II.
Although several generations exist between the characters, every member helps explain how Marty became the person audiences follow throughout the trilogy. Some additional family members have since been added in Back to the Future games and the animated series, but these are not official canon and therefore have not been included here.
Seamus McFly
Seamus McFly appears in Back to the Future Part III as Marty's paternal great-great-grandfather. Living in Hill Valley in 1885, Seamus is among the earliest members of the family shown on screen and is portrayed by Michael J. Fox. He is married to Maggie McFly and is the father of William McFly. Seamus's name would be given to Marty as a middle name, presumably by George.
Unlike later McFlys, Seamus refuses to be intimidated by Buford Tannen. His calm approach to conflict contrasts with the tendency of future generations to react when challenged. In many ways, he represents the version that Marty eventually learns to become by the end of Back to the Future Part III.
Maggie McFly
Maggie McFly is Marty's paternal great-great-grandmother and is played by Lea Thompson. She is the wife of Seamus McFly and mother of William McFly. Her most notable feature is her resemblance to Lorraine Baines McFly, who is also played by Thompson.
While Maggie is not biologically related to Lorraine, franchise co-creator Bob Gale jokingly explained that McFly men appear genetically predisposed to be attracted to women who resemble Maggie. Her presence also helps create a visual link between the 1885 and 1985 storylines. Seeing Thompson in both roles reinforces the cyclical nature of the McFly family's history.
Martin McFly
Although Martin McFly never physically appears in the trilogy, he remains an important figure in the family's history. He is Seamus McFly's brother and therefore Marty's great-great-great-uncle. According to Seamus, Martin was stabbed to death during a confrontation before the events of Back to the Future Part III.
Martin was killed because he refused to back down from a confrontation in case anybody thought he was a coward. This is introduced as a major plot for Marty McFly in Back to the Future Part II. Learning of Martin’s death gave Marty the drive to finally buck this trend and improve his future in Part III.
William McFly
William "Willie" McFly is the son of Seamus and Maggie and the great-grandfather of Marty McFly (and therefore the grandfather of George McFly). In Back to the Future Part III, William appears only as an infant living on the McFly farm in 1885, and as an adult in a photograph. As an adult, he is likewise played by Michael J. Fox, with Marty commenting on his good looks.
Despite his limited screen time, William occupies an important position within the family tree. He serves as the bridge between the pioneering generation represented by Seamus and the twentieth-century McFlys that eventually produce George and Marty.
George Douglas McFly
George McFly is Marty's father and the most important member of the family tree outside of Marty himself. Portrayed primarily by Crispin Glover in the original Back to the Future, George begins as an insecure, awkward man who is routinely bullied by Biff Tannen. The movie's central plot revolves around Marty helping George gain the confidence necessary to stand up to the bully Biff and pursue Lorraine in 1955.
In the original 1985, George is a timid office worker trapped under Biff's influence. In the revised timeline, George becomes a successful science-fiction author. George was played in both sequels by Jeffrey Weissman.
Lorraine Baines McFly
Lorraine Baines McFly, played by Lea Thompson, is Marty's mother and George's wife. She is first introduced as a frustrated and unhappy parent in the original 1985 timeline before becoming one of the trilogy's most significant characters. In 1955, Marty encounters Lorraine as a teenager and accidentally becomes the object of her romantic interest. The resulting storyline drives much of the first movie's comedy and tension.
Lorraine’s family also appears in Back to the Future in 1955, including her parents (Marty’s maternal grandparents), Sam and Stella. Her siblings are also seen briefly, including Mary’s Uncle Joey, who is incarcerated in Marty’s original timeline.
David Tiberius McFly
David "Dave" McFly is George and Lorraine's eldest child and Marty's older brother. He is portrayed by Marc McClure throughout the trilogy. Dave's role may be relatively small, but he serves as one of the clearest indicators that Marty's actions have altered history.
In the original 1985 timeline, Dave works at Burger King and appears to have limited prospects. After Marty's successful intervention in 1955, Dave becomes a successful white-collar professional working in an office environment. The contrast between the two versions of Dave demonstrates how George's newfound confidence reshapes the entire family's future.
Linda McFly
Linda McFly is Marty's older sister and the middle child of George and Lorraine. She is played by Wendie Jo Sperber in Back to the Future. Like Dave, Linda exists primarily to show the effects of timeline changes.
In the original 1985, she complains about her dating life and appears stuck in a rut. In the improved timeline, Linda enjoys greater confidence and social success, working in a boutique and attracting significant romantic attention.
Marty Seamus McFly
Martin Seamus "Marty" McFly is the protagonist of the Back to the Future trilogy and is portrayed by Michael J. Fox. His middle name comes from his ancestor Seamus McFly, reinforcing the family's connection across generations.
Marty exists at the center of every major timeline change. His trip to 1955 transforms George and Lorraine's future, while his adventures in 2015 and 1885 help him overcome his greatest personal flaw: his inability to ignore insults to his pride.
The various versions of Marty seen throughout the trilogy highlight how fragile timelines can be. Alternate futures show him involved in accidents, family struggles, and professional disappointments. By the end of Back to the Future Part III, however, Marty chooses not to race Needles, preventing the accident that originally damaged his future. This creates a more hopeful outcome than the one previously seen in 2015.
Jennifer Parker
Jennifer Parker is Marty's longtime girlfriend and eventual wife. She is portrayed by Claudia Wells in the original Back to the Future and by Elisabeth Shue in Parts II and III. In the future timeline visited in Back to the Future Part II, she is shown as the mother of Marty Jr. and Marlene McFly.
Jennifer's future changes alongside Marty's. The version of 2015 initially seen by Doc Brown is ultimately erased after Marty learns to avoid the decisions that would have led to his unhappy future. As a result, Jennifer's ultimate life remains open-ended by the Back to the Future trilogy's conclusion.
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