Spider-Man is typically depicted as a loner with very few family members. Peter Parker's parents died when he was young, leaving him in the care of his Aunt May and Uncle Ben. However, after years with almost no family, Peter was shocked by the emergence of a long-lost sister.

Spider-Man's secret sibling was introduced in 2014's Amazing Spider-Man: Family Business, by Mark Waid, James Robinson, Gabriele Dell'Otto and Werther Dell'Edera. When Peter was ambushed in his apartment by a group of mysterious assassins, a car pulled up to rescue him. The woman in the car dragged him inside, immediately revealing herself to be Teresa Parker, Peter's sister.

Peter was initially very skeptical of his relation to Teresa. Peter's sister was adopted, never knowing her true parentage. Years later, she became a CIA agent, just like Richard and Mary Parker. Evidently, Teresa was investigating a criminal uprising in Europe, when she discovered that someone was targeting the children of the Parkers. During her investigation, Teresa learned that she was the daughter of Richard and Mary...and that she had a brother.

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Teresa took Peter around the globe, where they learned more about their parents while tracking down the mysterious vault that criminals like the Kingpin desired. Along the way, Peter and Teresa fended off several assassins, including the supervillain Cyclone. During one of these attacks, Teresa learned that Peter was Spider-Man. Eventually, Teresa and Peter arrived in Cairo, discovering the vault which only the Parker children could open.

The Parkers were ambushed, however, by the Kingpin and his men. Wilson Fisk revealed that he had Mentallo alter Peter's perception of Teresa and Teresa's own memories so that she would appear as his sister. Kingpin claimed that Teresa was in actuality Teresa Durand, a CIA agent with no connection to the Parkers. Despite this claim, Teresa aided Peter in defeating the Kingpin and the Sleeper robot which emerged from the vault. Ultimately, Mentallo mindwiped Teresa and the Kingpin, so neither one had any memory of the events which transpired. Disheartened by the loss of a potential sister, Peter returned home.

Teresa next appeared three years later in 2017's Peter Parker, The Spectacular Spider-Man #1, by Chip Zdarsky and Adam Kubert. Teresa had joined S.H.I.E.L.D. as part of the Gray Blade division. Once there, Teresa became a fugitive after stealing secrets about "Project Twilight." This project was a plan to take down both superheroes and super villains, a dangerous plot which Teresa deleted from S.H.I.E.L.D.'s files and hid in her bloodstream.

Teresa then sought the help of Peter, finally remembering who he was. Peter and Teresa practically became crime-fighting partners, investigating "Project Twilight" while fighting the Kingpin and the Vulture, among other villains. Teresa was outfitted with high-tech wings and non-lethal guns by the Tinkerer's brother, who supplied many heroes with their equipment. When the Tinkerer was revealed to have created this robot brother to sabotage superheroes, the Parkers took him down.

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Teresa then accompanied Peter and J. Jonah Jameson into the past, to retrieve information to defeat the Vedomi aliens. In the past, Teresa contacted Nick Fury, accessing files which confirmed her relation to Peter. Teresa also accompanied Peter to an alternate dystopian future, where they inspired an older Peter to become Spider-Man again before returning to the present and defeating the Vedomi. After turning herself in to the Gray Blade, Teresa eventually met Aunt May, although she didn't reveal that she was Peter's sister.

Although she hasn't been seen often, Teresa Parker adds another layer to Peter's backstory. Peter doesn't simply know that the Parkers were CIA and S.H.I.E.L.D. agents, he now has Teresa, a living relative who carries on in the family tradition. Teresa embodies this connection to Peter's past allowing him to interact with family, rather than simply long for his lost parents.

Most importantly, Teresa provides Peter with someone he can relate to and connect with. Spider-Man's life is often pretty lonely, with very few family members and friends who he can really confide in about the realities of his double life. With Teresa, Peter has a family member who knows all sides of him, and understands much of the "family business" herself.

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