Here are two characters from my story: Manta and Manta.  Yes they both have the same name.

In my story's universe twins are super ultra rare, because these characters are not born the same way that people are born. 
They either burst into existence with the invention of a new species or are reborn like a Phoenix after the previous character representing their species passes away.

Twins happen when something goes wrong in the reincarnation process and instead of one character being born it's two. 

These two represent the two different kinds of manta rays, being the reef mantra ray and oceanic manta ray respectively.

The boy (the one on the right) is the more prominent of the two within the story.

Here are some little sketches I did of him.

And here's his ref sheet