It has already been confirmed that Nihilus was a part of Exile that broke off at the destruction of Malachor V.
Someone needs to read the KOTOR Campaign Guide, or at least stop listening to ridiculous fanon theories.
"There is something going on in time and space, and beyond time and space, which, whether we like it or not, spells duty." -Winston Churchill
"For of all sad words of tongue or pen, The saddest are these: 'It might have been!'" -John Whittier
"Apathy is death." -Kreia