Can a Zen Master know about your past lives?
The book, Wanting Enlightenment is a Big Mistake, the Teachings of Zen Master Seung Sahn (ZMSS), is an excellent book in many ways. In a story in the book named "Karma Talking", ZMSS describes a story where a Zen Master told an emperor and the emperor's wife about their past lives.
The story begins:
I am the emperor, what kind of past life did I have before I was born as the emperor?
The Zen Master perceived his mind for a few moments, and said, "In a previous life, you..."
and he went on to tell the emperor about his previous life.
He did the same thing for the emperor's wife, but the wife did not believe him. Angry at the Zen Master for what he had told her, she argued with him, and the Zen Master replied:
If you do strong meditation practice, you will be able to perceive your own past-life karma.
I don't want to give away any more about this story, so I'll leave it at that.