The next section includes spoilers for the currently available third issue of DC vs. Vampires: AllOut War.To put it mildly, Nightwing’s ties with his former friends are problematic. He is obviously hell bent on creating a new world order for his people, but he still has unresolved sentiments for hisliving relatives.
This becomes even more clear when it is revealed in DC vs. Vampires: All-Out War #3 (written by Alex Paknadel, Matthew Rosenberg, Pasquale Qualano, Nicola Righi, and Troy Peteri) that Nightwing did not place a bounty on Damian’s head despite trying to assassinate him.
This shows that Nightwing still has feelings for his younger brother and is probably the same way with the rest of his family. Examples of this include his offer to change Alfred. After his change, he yet retains a darkness and cunning. It’s certainly plausible that Nightwing spared Damian for his own purposes rather than out of love.
Deathstroke asked Azrael, a former vampire, to establish whether Batwoman is actually an adversary of the vampire realm when she volunteered to join him and his crew. Damian, who had taken the more heinous decision to attack the king, was mysteriously exempt from a bounty on his head, according to Azrael, despite the fact that there was one on her head. Nightwing never went after Damian for retaliation, therefore this tiny fact helps to explain why Damian has had so much agency in the universe despite his acts.
After Damian’s failed assassination attempt, Nightwing did acknowledge he still wanted Damian to be alive. He may have been attempting to forge some sort of understanding between vampires and people, but he had a sneaking suspicion Damian would be involved. From the outside, he thought Damian was unique among vampires because of his inherent goodness, which helped to balance the worst aspects of being an undead person. Maybe this is a continuation of that. Damian would need Nightwing to let the past go in order for him to survive and prosper.
There is, of course, another possibility. This is still the same person that led Batman astray for so long before fatally stabbing him. Anyone can speculate as to what Nightwing is thinking at any given time given his undead status. Damian being allowed to survive may have a darker purpose. He acknowledged that there is a hierarchy, but Damian would not be the heir apparent if Nightwing were to perish. He did not, however, state that Damian was not the next in line.
Nightwing might be planning for the future. Perhaps he genuinely think what he’s doing is important, but he also knows that people will never submit to his authority voluntarily. So, if they do manage to kill him, it will probably completely destroy the vampire social structure. Maybe that will bring about the peace that Nightwing seeks by trusting the Robin he helped create if Damian is secure on the other side and free to take control once the dust settles.