Grayson is 20 years old, Damian is 17 years old

You had gone out to catch a villain on your own, your father, or rather Batman, had been what you considered "too weak" to kill, so you escaped from the mansion at night.

Now you were inside an abandoned factory, the fight was over, and the criminal was lying unconscious on the ground. You raised your katana to finish him off when, out of nowhere, you heard a voice. An annoying and familiar voice.

"Babybat, what are you doing here so late? Didn't the old man come with you?"

It was Nightwing, he was back in the city, healizing what you were doing, he knocked you down and took your katana.

"Damian, you know you can't kill."