He appeared to back up the claims that Blanket was not speaking — but said the problem dated from long ago.
He said: "He kept himself to himself. He would just immerse himself in his own little world."
Lester also talked about how Blanket is kept hidden away by the Estate saying: "The Jackson estate don't want him to make money for anyone else. He's an heir to a billion-dollar trust.
"They have trust issues, especially with people who may think they want to take advantage of either Blanket, Paris or Prince (Blanket's 22-year-old brother) for their own financial gain.
"When you get super-wealthy you become very guarded and very mistrustful of a lot of people. It's just sad that this money issue would get in the way of them actually being able to have good friends.
"I would just like to reach out," he said, but added: "It would be a bit like you picking up the phone and going, 'I want to go and see the Queen'. You have to go through various channels."
Blanket was given his nickname by his father, who was inspired by the character Linus in cartoon strip Peanuts, who always carried a blanket with him.
Blanket was homeschooled before his father's death and is now at a private school. He is not allowed on social media and any photo featuring him is heavily vetted before being released by family members.
HBO's Leaving Neverland will air on TVNZ 1 on Sunday March 10 and Monday March 11 at 8.30pm and on TVNZ OnDemand.