The teen angst of a young Prince Black Bolt - unable to verbally express any of the emotions that are churning inside him, he would be full of ennui, ennui that is only lifted by the time he spends with Medussa who he never feels worthy of.
It doesn't help his confidence that his brother Maximus whispers venom in his ears and undermines his elder brother every time he can. Black Bolt too is fearful of all the power he has in one whisper.
Gorgon and Triton would be the teen athletes who like to bash and smash but who have to learn restraint, especially when one of them injures Lockjaw in one of their playfights. Gorgon has to learn that he can't ever let his powers get out of control lest he injure someone close to him. He must control his emotions and learns that through the pain that his actions have caused those he loves most - especially Crystal who becomes both angry and fearful of him.
Karnak of course would be torn between logic and emotion. His own love for Medussa blinds Karnak to the way those feelings are being manipulated by Maximus who seeks to claim the title of crown prince for himself.
When a crisis threatens all the Inhumans, Black Bolt has to stand up and fight or everything will be lost. He thinks he will fail and stand alone but he is wrong. The whole story is about how these cousins banded together, put aside their doubt, fears and mistrust and do what they had been trained to do - LEAD AND PROTECT.
I just found these images and loved the concept so much that I scratched out a quick plot. Inspiration is where you find it. I think my story is fresh and fantastic.