If you read the thread (and *ahem* the links therein) you will see that it is proven to a limit that Kreia and Kae were one and the same.
Not sisters.
(It is always a good idea to read a thread before commenting.)
There was a "final" feud that I was referring to, when the game was finished, but VU didn't want to sign off on it because of the courrt case ... so Valve released the game to the magazines for preview, and the whole ugly truth came out ...