Charles DiLaurentis is “A” and Jason’s Brother

Turns out Mona’s anagram was a code for “Charles DiLaurentis”.  In “Welcome to the Dollhouse”, Spencer finds alphabet blocks in the house they are trapped in.  She realizes the blocks spell out “Charles”. 

We also saw an old family video of Alison’s mom holding a baby girl.  She tells two boys to kiss their sister.  Does Jason have a brother, possibly a twin?

http://whoisontheateam.tumblr.com/post/114568786247/prettylittleliars-jason-and-charles

We don’t know of any characters named Charles, but that doesn’t mean we haven’t already met this character.  PLL showrunner Marlene King tweeted “Are you sure Charles is not a cast member you have already met?”

Are you sure Charles is not a cast member you have already met? @brickbyb #askmar
— I. Marlene King (@imarleneking) March 25, 2015

And we should have enough hints to figure out who Charles is.  Marlene also tweeted “I have given you a ton of hints in seasons 3-5. A is not a stranger.”

I have given you a ton of hints in seasons 3-5. A is not a stranger. @caitlyn10312001 #askmar
— I. Marlene King (@imarleneking) March 25, 2015

Who do you think Charles is and why do you think he's been tormenting the Liars?