Board Thread:Warhammer 40k General Discussion/@comment-202.67.108.41-20140425072251/@comment-86.101.227.61-20141128123033

Only 8 Astartes were used to start the Grey Knights, these came from both traitor and loyal legions "alike". Janus, Epimetheus (Dark Angels), Khyron but this contradicts from some of the HH books. http://www.bolterandchainsword.com/topic/225880-who-were-the-original-8-grand-masters/

Anyway, a maximum of 8 Astrates found a new life in the Grey Knights, probably only 4 from the traitor legions.

Deathwatch was made ... compliacted! Wiki says during the HH with Garro and Lexicanum says by the inquisitors some time after the HH without Garro. http://wh40k.lexicanum.com/wiki/Deathwatch

http://warhammer40k.wikia.com/wiki/Deathwatch

There seems to be some crossover in where the Garro from the Flight of the Einstein ended up either starting as a Grey Knight, Deathwatch or neither.

Ultramarines did not take any of the HH traitor legions but there are vague hints of their numbers swelling, when the forgotten and the purged are lost to records.

Grey knights had their gene seed removed and replaced by GK gene seed. So I imagine something similar can be done if traitor legions were grouped together?

I think there isn't a definite answer, GW want as many mysterious and speculation as possible. They have liked some stories and approved them but within the stories they approved there are canon conflicts. Also there's the slight problem that we are looking ten thousands years into the past..from a postion thirty nine thousand years in the future.