It's not only 'A' that's going to steal the show on ABC Family's smash hit TV series "Pretty Little Liars". Every real fan knows exactly that 'A' is the main mystery in the plot, but a twin has significant role in the story. The question now is that, "Who has a twin?"

In the books by Sara Shepherd in which the teen mystery series has been based, Alison, portrayed by Sasha Pieterse, is the one who has a twin. So, this is not surprising if PLL viewers think that the former queen bee literally has her double.

Unfortunately, Alison in the TV series doesn't have a twin sister. Some others took their wild guesses on who really has a twin sister or a brother. They even thought that Toby and Spencer, played by Troian Bellisario, were twins, while some feels that Jason DiLaurentis is the one who has a biological look-a-like.

However, it seems that the guessing has suddenly focused on one person: Keegan Allen. Allen plays the character of Toby Cavanaugh in the "Pretty Little Liars" TV series. Tammin Sursok's latest post on Instagram is more or less implies that Allen might be also playing the new, unknown character James Neilan.

Do you wonder why most think that Toby and James are twins? Sursok, who plays Jenna, posted a photo of PLL read with cards placed in one table seat: Toby Cavanaugh and James Neilan.

Another twin theory has came up when Tammin revealed, seemingly confirming that the TV show will finally bring the twin character as the season continues to bring more mystery to the character of 'A'. She didn't just give a "twin" clue but a "twin sister". It means that anyone who has a secret twin will be a girl. The name Jason DiLaurentis becomes top on the list who possibly has a twin sister.

At least, the twin theory has been trimmed down to two (Well, let's hope so). "Pretty Little Liars" viewers will just have to wait for the perfect, perhaps shocking as well, revelation in the upcoming episodes.