Could the younglings that Anakin didn't actually kill became the knights of ren?

It actually accomplishes the opposite effect. There are few crimes that people find as horrible as someone murdering children. I mean, people who do stuff to children (murder or worse) have a large tendency to get the Sith beaten out of them by their fellow inmates. Hell, Wes Craven made Freddy a child murderer in life since that was the most vile thing he could think of!
Also, don't forget the timeline of events. Anakin actually showed some actual remorse for his part of the death of Mace (unlike the token show for Dooku or the complete lack of it for the Tusken village). Ten minutes of screen time later, in his first act as a Sith Lord, he kills children.

This too much evil, too quickly, hurts Vader's redemption in Jedi.

 

--- Double Post Merged, Jun 20, 2016, Original Post Date: Jun 20, 2016 ---

ok. . . .