Inside, the liars discover that Big "A" is named Charlotte DiLaurentis. CeCe/Charlotte reveals herself as "A" and tells her story; saying that she is transgender, was formerly known as Charles DiLaurentis, and became "A" because the Liars were happy that Alison was gone.
During the first half of the sixth season, Charlotte's history as Charles and "CeCe" is explored before eventually being revealed in "Game Over, Charles" when Charlotte is unmasked as "Big A." She is eventually stopped by the Liars before she can commit suicide and declares the ending to her reign as "A".
Game Over, Charles
It's revealed that Charles DiLaurentis is, in fact, Charlotte DiLaurentis, alias CeCe Drake, and he transitioned at the age of 16.
Charlotte had learned from Jessica how to change her name and lie about her identity to fit right in with her family, so Charlotte believed employing these skills would come in handy for the "A" game, which would be a great chance for her to finally succeed at something after being told she was a failure for the way ...
As the girls witness Alison discovering Jason and Mr. DiLaurentis's unconscious bodies, they realize she's alone with "A," who is revealed to be CeCe Drake (Vanessa Ray).
A turned out to be CeCe Drake, the adopted sister of Alison DiLaurentis, who went missing and was presumed dead by the end of the show's pilot episode.
Why did CeCe create the dollhouse? She kidnapped the liars because she viewed them as her dolls. To Charlotte, the Liars belonged to her and her only. She wanted to play with them forever, but knew she needed a secure place to hold them.
"A" turns around and is revealed to be CeCe Drake, who reveals that she was born as Charles before transitioning into Charlotte. CeCe/Charlotte reveals that she became "A" (and thus Red Coat) in order to sneak out of Radley and because she was angry that she thought the Liars were happy about her disappearance.
Mary then cradles Spencer's body and reveals that she is indeed Spencer's mother, making Spencer the biological sister of Cece Drake.
Alex is the younger sister of Charlotte DiLaurentis and the twin sister of Spencer Hastings.
Melissa was unaware of Spencer's adoption and thought they were biological sisters. They are actually half-sisters, as they share the same father but different mothers. They are also adopted sisters since Veronica adopted Spencer. They share a half-brother, Jason DiLaurentis.
Courtney DiLaurentis was the identical twin sister of Alison DiLaurentis. She was also the girl who Aria, Spencer, Emily, and Hanna knew as "Ali" and was their best friend. She was actually not mentally insane, Alison just made a plan to make Courtney look like it.
Spencer Hastings
Spencer discovered that her father Peter (Nolan North) had a one-night stand with Mary Drake (Andrea Parker), believing that she was actually her identical twin Jessica DiLaurentis. That hookup led to Mary becoming pregnant with Spencer, and the Hastings adopting her after her birth in Radley.
Just as the Liars are being brought to jail, CeCe kidnaps them and tortures them inside the Dollhouse. Inside, the liars discover that Big "A" is named Charlotte DiLaurentis.
Officially introduced in the series finale, Alex Drake is both the identical twin of main character Spencer Hastings and the previously anonymous identity known as "A.D." In childhood, Drake was adopted by a wealthy British family that later abandoned her, forcing Alex to bounce around foster homes and orphanages.
To protect Charlotte DiLaurentis after she supposedly killed Alison. To get rid of her twin sister Mary Drake.
ALISON AND BETHANY ARE TWINS. Bethany is the equivalent of Courtney. In the books, Alison and Courtney are twins, and Alison is jealous of courtney so she pretends to be her and gets her sent to radley.
Aria Montgomery is the 9th A to be revealed. Joined in Power Play. She only joined to protect her friends and prevent her file about Ezra from getting out. Was also being blackmailed by A.D. to trash Emily and Alison's nursery and place the recording of Peter Hastings and Jessica DiLaurentis in Spencer's house.
Peter Hastings is the father of Melissa, Jason, Spencer, and Alex Drake. He had an affair with Jessica DiLaurentis which resulted in the birth of Jason DiLaurentis. He also had a one night stand/affair with Mary Drake (who he thought was her twin sister, Jessica), which resulted in the birth of both Spencer and Alex.
Mary could have been a woman on the autism spectrum scale, and CeCe could have had narcissistic personality disorder (she makes the transition from boy to girl look seamless and glamorous, which is a far cry from the reality of true trans teens).
Soon, Charlotte adopted the name Cece Drake, to conceal her real identity from her siblings, Alison and Jason, whom she wanted to get to know. After meeting Mona in Radley, Cece was so intrigued by her games, she had to try them out for herself, and uber A was born.
CeCe really did kill Wilden -- he knew Ali was alive -- and she sent in Sara to see the body IRL and make sure he was D-E-A-D.
CeCe was trying to protect her family from Bethany when she struck Ali in the head. Bethany used CeCe's clothes to escape Radley, and was headed to hurt Mrs. Di after discovering that she was having an affair with her dad.
On screen, we see Noel creeping into a room where Spencer was sleeping, and he pours blood all over her. Remember when Spencer woke up in the dollhouse, covered in blood, convinced that she had hurt someone? It was just NOEL FREAKING KAHN messing with her this whole time.
Alison was unaware that CeCe Drake was actually Charlotte until "Game Over, Charles" when Charlotte revealed herself. Ali found out that she had another sibling in, "Game On, Charles", and heard a portion of the story in "Songs of Experience"/"Don't Look Now". Alison advocated for Charlotte's release from Welby.