This goes for anyone. The story does not have to be a book. It can be a videogame, a movie or... Well.... Anything really. If you r having a hard time coming up with a legit reason for an occurrence in your story then contact me!
Read hero.com it shows how superpowers can be conduited by objects as so the objects take on the properties of the powers like capes of flight and cloaks of invisibility or lightning guns.
Maybe they have Kryptonian roots or r waterbenders. As for absorbing the sun r you saying they can photosynthesis? Because that would mean they have Chlorophyll in them which also means that they r green skinned. Perhaps they r the link between humans and plants!!!!