TONIGHT! TONIGHT! TONIGHT! I could not be anymore excited that the new episode premieres tonight and of The Vampire Diaries. On twitter I hear people are going to try and get "The Secret Circle" and "Dark Cassie" trending worldwide today, so make sure to join in if you're on twitter! I am, and you can follow me @ShiviSilva.
As for who the other Blackwell child is...here are my thoughts. Beware, it's a tl;dr.
- Faye gets her Chamberlain blood from her father, Thomas Chamberlain, who's father was Henry Chamberlain. If Faye had to be the other Blackwell child then that would mean Dawn has to have some sort of Balcoin/Blackwell blood in her and her obsession with Cassie's father may not have been an attraction but more of an admiration.
- Diana is a Meade from her father's side of the family. This is known because Charles's mother is a Meade. For Diana to be a Blackwell child then there are actually two possibilities here.
--- Kate had an affair with Samuel Blackwell, the father of John Blackwell. Therefore Charles would actually have the Balcoin bloodline in him making Diana another child of a Blackwell.
---On the other hand, Diana's mother could have had a family relationship with John Blackwell either as a sibling, cousin, or distant family member linking to the Balcoin/Blackwell family tree.
- Melissa gets her Glaser bloodline from her mother's side of the family. The reason I figured this out is because in Episode 5, Slither, she said to Nick that she found her mother's diary and it spoke of hiding her family Book of Shadows in the forest. Now each of the six families has a Book of Shadows, therefore if the Glaser BoS belonged to Melissa's biological mother, that would mean Melissa got her Glaser bloodline from her mother's side. Meaning for Melissa to be the other Blackwell child, all that had to happen was John Blackwell had an affair with Sophie Ann Glaser (Melissa's mother) and the product of such an action was Melissa.
- Adam, I'm pretty certain is not the other Blackwell child. Chris Zylka in an interview at the Water Project said that the only one for sure who wasn't this other child is Adam, Thomas Dekker's character.
- As for Jake and Nick, I'm not sure where they gets their Armstrong family blood from, whether it's from their father's side or mother's side. However, I'm thinking that the writers won't go with Jake as the other child of Blackwell if they want a love triangle between him, Adam, and Cassie. Of course, I would never rule out the possibility completely.
Based on everything said here, I actually think the other child of Blackwell could possibly be Melissa, the underdog of the Circle. It wouldn't be hard to explain that John Blackwell had an affair with Melissa's mother and it would also open up a whole new interesting storyline for Melissa. And to say the least, Melissa is the least expected out of all the girls.
However, there is always the possibility that this half-sibling could be someone we just haven't met yet. Remember, the binding ritual doesn't only bind the six members together, it binds their bloodlines. Therefore, this person, if they share the Blackwell blood with Cassie is indirectly apart of the circle.