When Kader actually ended up becoming a Knight of Ren at first he didn’t feel too comfortable with the idea. Yes, his father is a Sith, and he knows this, but the problem is that he… still wanted to be a Jedi for the longest time.
However, those thoughts were washed away the moment he had to make a choice that was either life or death.
Kader doesn’t have too many true friends. He has his fellow Knights as well as Kylo, but he doesn’t classify them as friends.
In truth, the only one he could ever consider a friend would be @arabella-of-the-first-order due to the fact that she’s the only one he can speak with. Not to mention that they have a relationship that his father doesn’t know about.
Mostly friends are tools, they are to be used, and then disposed of. Obviously, he has several contradictions of the idea of what a friend or friends are, but for now he doesn’t feel that he needs any.
Kader was ironically named after Darth Vader… mostly due to the fact that Wyndel is horrible at Names at that was the best one he could come up with (And he also lost a bet big time).