Hey, I've read that book too! And Cat Tails, it's NOT FAKE!
The book was made by disney, but it was used for
storyboarding the lion king movie. It was called The Lion's
Pride" or something like that. It was actually pretty good.
Glad I could help, cause it seems that everybody else has
their head stuck up their....well, never mind.

ACTUALLY if realated lions mate that could tragically effect
the cubs plus if Scar WAS nala's father 1.she would look
like him 2.she would be evil 3.Disney wouldnt allow it!

Case and point:The story you read is FAKE

I_LUV_TLK -> You know, if you knew ANYTHING about Lions, you
would know that THEY DONT CARE. They MATE with each
other. No one CARES if they are related. Think what you
want, but that is the cold hard facts of the animal world.
NO ONE CARES. Period.

Oh, and for you
believers in God, if Adam & Eve were the only two humans on
earth to begin with, how do you think they all multiplied?
By mating with magical people who suddenly came out of no
where? So the next time you go on a date, think about how
your related to that person, in a VERY distant way.

Check out this:
http://www.freewebs.com/nalassite/whoisnalasfather.htm Now
what?

Perhaps Someone confused The Lion King with Bambi?

I don't believe that Simba and Nala are cousins. My first
reason being that why would family mate with each other.
Secondly that would make Scar Nala's father and I personally
believe that Nala's father was from another pride. So I
think that the novel you heard about is false.