<P> In Back to the Future, Lorraine is initially portrayed in 1985 as middle - aged and unhappy . After Marty changes the timeline, she is shown to be fit and happily married to George in 1985 . In Part II, she is still happily married to George in 2015, but in the dystopian alternate 1985 timeline she is widowed and married to Biff . </P> <P> David "Dave" McFly (portrayed by Marc McClure) is the eldest child of George and Lorraine McFly . In 1985 before Marty went to 1955, Dave works at Burger King, but in the post-time travel 1985 he wears a suit as a nondescript white - collar worker for an accounting firm . In a deleted scene from Part II, the alternate 1985 timeline shows that Dave is an alcoholic and a gambling addict following George's death and Lorraine's second marriage to Biff . </P> <P> Linda McFly (portrayed by Wendie Jo Sperber) is the middle child and only daughter of George and Lorraine McFly . In 1985 before Marty went to 1955, Linda is having boy trouble and it is unknown if she is in college or has a job . In 1985 after Marty went to 1955, Linda works in a boutique and has gained the attention of many boys . </P> <P> Seamus and Maggie McFly (portrayed by Michael J. Fox and Lea Thompson) are Irish immigrants and the paternal great - great - grandparents of Marty McFly . In Part III, Marty is befriended by Seamus and Maggie . While Maggie does not trust the "strange young man", Seamus has a familiar feeling about him and believes that helping him is the right thing to do . They have a son named William (Marty's great - grandfather). Much like his descendants, Seamus is harassed by a member of the Tannen family, Buford Tannen . </P>

Marty mcfly's sister in back to the future