Keith will likely be defiant. He has a strong sense of justice and will not be easily broken by Zarkon. He might try to fight back immediately if he has the chance.
One of the main characters could be Shiro. Shiro has always been like a big brother to Keith. So when Keith turns into a girl, Shiro would be there to help him adjust. He'd make sure Keith is safe and comfortable in his new form. Also, Hunk could be a main character. Hunk would probably be the one to offer emotional support and cook some comfort food for Keith during this tough time of adjustment.
There's not enough information given to really know who Kevin Will is in the 'end of watch the kevin will story'. He could be anyone. He might be a character in a fictional story, in which case his identity could be shaped by the plot. For instance, if it's a mystery story set around a night watch, he could be the detective or the person who holds the key to solving the mystery. Or if it's a more personal story, he could be someone going through a life - changing experience during his watch. But all of this is pure speculation at this point.
I'm not sure if there is a specific 'pregnant Keith fanfic' available. It depends on the fandom and the amount of fan - created content out there. You could try searching on popular fanfic websites like Archive of Our Own or FanFiction.net.
Kevin Cummins might be an individual with a passion for storytelling. Maybe he is someone who uses his stories to convey important messages, entertain people, or preserve a certain culture or tradition. Without more context, it's difficult to say exactly who he is.
One common theme is friendship. Kevin and Gwen's friendship is often explored, showing how they support each other. Another theme is growth. Kevin's growth as a character, whether it's in terms of his powers or his personality, is frequently a part of these fanfics.
I think Keith's closest friends within the blades are most affected. If he's younger, they might become more overprotective. If he's older, they could start relying on him more for advice. For instance, if there's a character named Lance who was previously on equal footing with Keith, now he might see Keith in a different light depending on his age.