Unique boy names for a story?

You should consider how things reflect upon the other characters. For instance, you can see the sky with your eyes, but you can't see truth in the same way. It takes more effort, so using the name True would in a sense be ironic. Jemma is the most vivid to me, based on your description, yet having the least obvious name. I think for the boy you need an even more obvious name than Sky, such as Forest, Tundra, or even Barren (depending on the setting). Very down to earth, "obvious" name residing within a very emotionally deep "unobvious" character.