If you mean the brother's statement about seeing "someone" stab Joe Clyde with a knife then I suspect those 5 terabytes of discovery includes information about it.
IIRC Joe Clyde's brother is two years older which would have made him 7 at the time of the disappearance. A lot of factors could have caused him to make his statement - including that he really did see someone stab Joe Clyde - and it's likely the TBI and FBI have conducted forensic interviews with him.
At face value I'm inclined to believe Joe Clyde wasn't stabbed that night since nothing has been released about blood evidence in the house other than Joseph's blood on the shovel. Results of the testing for mitochondrial DNA on the hair found on the shovel hasn't been released.
What caused the brother to make the statement is anyone's guess: was he threatened, manipulated, did he create a "memory" in order to block out the reality of something he witnessed? Have the authorities talked to him again now that he's 9?
Joe Clyde Daniels: 10 things we learned at preliminary hearing
To add:
Krystal's August 2019
letter to reporter Nick Beres made no mention of someone other than her and Joseph being in the house. Her letter appears to be in response to
Joseph's July 2019 letter to his parents where he accused her of suffocating Joe Clyde and threatening him with a knife when he tried to intervene yet her only mention of it was saying it was one of the reasons she is divorcing him.
[
Joseph's October 2018 letter to his parents accused her of being responsible for Joe Clyde's disappearance. He claimed Krystal had help from someone but said the person picked Joe Clyde up alongside the road. He also said he believed Joe Clyde was alive.]
Sorry for the lengthy response. As you can see
I too have tried to analyze the brother's statement to see if there is merit in it and in the end *none* of claims by anyone who was in that house subsequent to the original confessions by the parents make sense. No pattern arises, no dots connect. This is all my own opinion and subject to change in the future.