Well, in the book, he didn't compare his childhood anything remotely
like being the boy in "The Sixth Sense". In fact, all he ever did was
try doing a seance, for fun, I think with a friend, and something
about it frightened him (as far as I can recall). Then I think he had
plans to become a priest, but for some reason didn't. Then, he said,
I think both in the book, and at a reading/seminar of his I attended,
that a medium had told him that he himself would also become a medium,
which took him completely by surprise.
Now, I would think that if, since childhood, he'd been communicating
with spirits like the boy in "The Sixth Sense", a career as a medium
would be no surprise at all. Equally, he'd never had needed to try a
seance if he was already communicating with spirits anyway, and the
seance shouldn't have been a frightening or alarming experience.
I'm not putting him down in any way - I believe he is a genuine
psychic at the very least, and probably does have the ability to
communicate with spirits, although I'm not sure as to what extent.
A very good clairvoyant/psychic can easily read from a living person
details about a deceased loved one and claim to be a medium in contact
with the spirit of the deceased loved one. So, I'm not entirely sure
of the extent of James Van Praagh's mediumistic abilities, although I
do believe he has some to at least a certain extent.

Edgar Cayce did make vague astrological references in his trance
states, but he was no astrologer. And I don't know if Nostradamus was
really a trained astrologer, either. And the "Scriptures", while
containing some astrology (as well as condemning anyone who'd practice
it), is certainly no astrological textbook.