So basically I think Charles Dilaurentis (A) is either Jason's twin brother or Alison's 'not-big-as-Jason' type big brother. This makes sense until I start questioning what happened to Charles and why he wants to turn his sister (Alison) and her friends(Aria,Spencer,Hanna,Emily) lives into a living hell. Which this brings the situation into a whole new level when we realize 'A' killed Jessica Dilaurentis. Why would any son kill his own mother by burring her ALIVE. If, Charles is Jason's twin brother, then this means that he is also Spencers half-brother. Which this leads to the question, if Melissa Hastings knew about 'A's identity. Well this didnt turn out as a theory that much but this is what I mainly think.