The Identity of "A" Was Finally Revealed in the "PLL: Original Sin" Season Finale

Turns out, Rose wasn't just pregnant with Angela. She gave birth to twins, and named Angela's brother Aaron. Angela's sibling didn't attend Millwood High with Angela because Rose believed he had a face "only a mother could love," according to Clanton. After Angela's death and Rose's mental breakdown, Clanton raised Aaron in secret, and they worked together to avenge his sister.

At the end of episode 10, an injured Aaron escapes from the local hospital and goes to Chip's house to kill him for raping Tabby and Imogen. While it's unclear if he succeeds in killing Chip, it's obvious that Aaron will be on the loose if "PLL: Original Sin" is picked up for another season.