"How do you know I have a brother?" Cal wasn't playing anymore.
"You always do. Or a cousin or a best friend bonded by blood."
While admittedly a "twist", the reincarnation aspect also seemed to largely devalue the scope of the story without adding
The flashbacks to 12 years ago, narrated by a 15 year-old Niko, were easily the best part of the story. Seeing more of Niko and how he and Cal were when they were younger is always a treat. Niko did sound pretty much identical to his older self. A bit more variation would have been beneficial.
So, there are the murders and the the evolution of their characters. In the present day, Cal is devolving further and further, making for a depressing read. He is willing to fight himself from going too far for Nik's sake, but it is getting close.
Grimm does not make an appearance, although the threat that he represents is referenced often.
It was important for Cal to see Niko completely lose it, just the once.
"That fifteen-year-old kid was my hero and no one, not even you, gets to say shit about him, all right? He was a hero and there is nothing he did or didn't do that will ever change that" - Cal to Niko
Content warning: language, sexual references, etc. You have been forewarned.