There are a ton of suspicious characters on Pretty Little Liars, but if there's one person who is a total question mark, it's Sara Harvey. The shower-obsessed Rosewood resident entered the Liars' lives as an ally and the only other person who could understand what living in Charlotte's dollhouse was really like. Of course, after it was revealed that Sara was working with Charlotte the whole time, it seemed like all of Sara's stories of torture at Charlotte's hand were just that — stories. Now that Sara is lurking around Rosewood after Charlotte's murder, it's making the former Red Coat all the more suspicious. What is Sara's connection to Charlotte, other than simply aiding her in torturing the Liars? Maybe it's a simple one: Sara could be Charlotte's biological sister, and it's one theory that could make their partnership make sense.
The idea that Sara could be Charlotte's sibling and not also Alison's only really became possible after the Season 6 finale. It was revealed in "Hush, Hush Sweet Liars" that Charlotte is the biological daughter of Mary Drake, Jessica DiLaurentis' twin. That makes Charlotte and Alison biological cousins, not sisters, and leaves room open for Charlotte to have siblings that aren't just Alison and Jason. When you consider the physical similarities between Charlotte and Sara, it actually makes a lot of sense that they could be biologically related — and it also begins to fit some of the stranger pieces of Sara's story together.
We know that Sara had a rough home life, and that she ran away because her mother is an abusive alcoholic. We've never met Sara's mother, so it's possible that Sara didn't run away from her biological mom, but from her foster or adoptive mother instead. Perhaps she wasn't kidnapped by Charlotte at all — instead, maybe she found out that Charlotte was her biological sibling, and decided to join her in all of Charlotte's A adventures. After all, if Sara's home life was so miserable, she might have jumped at the exciting chance to play Charlotte's partner in crime — especially if, like her friend Claire said, Sara had a bit of mean streak herself.
How could Sara be Charlotte's sister and not know it until she's older? Maybe it's because Mary gave birth to Sara while Mary was still in Radley. We know that Charlotte was adopted by the DiLaurentis family shortly after her birth, but it's very possible that Mary could have had a second child while she was a patient in the mental institution. Since Sara is Alison's age, it's doubtful that the DiLaurentis family would have wanted to take in another one of Mary's children, especially since Charlotte was not welcomed into the family by Kenneth. Maybe Sara ended up in a bad home situation because the DiLaurentis family wouldn't take her in, which allowed her to justify the cruelty that she and Charlotte brought upon Alison and her friends.
Sara being Charlotte's biological sibling might also explain the reason why Sara was wearing Alison's yellow top in the dollhouse. Maybe it wasn't Charlotte who dressed Sara in those clothes, but Sara herself. It would also explain the odd scene in Season 6 between Sara and Alison. Sara tells Alison that they both knew Charlotte "like a sister," and maybe Sara wasn't being as metaphorical as we assumed.
If Sara is really Charlotte's sister, she might be able to give us even more answers about Mary and the rest of Charlotte's twisted backstory. We'll definitely need it going into Season 7.
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