Enderians came to be from the humans who had settled The End living there for a multitude of centuries. Slowly evolving with their diet of Chorus Fruit to develop the ability to teleport.
Eventually even gaining the Endermens rage to an extent.
As the race continued along its path, they began developing mutations relating to its environment. Such as the Oculus mutation and the Draconian mutation.
However due to their human ancestry, Enderians are not always predetermined to look similar to endermen, some still appearing to be mostly human.
However, those who look the most like endermen are considered “Pure” to an extent, as their entire bloodline seems to have lived and grown in The End.
Enderians generally have a lifespan of 200 years, aging at half the speed normal humans do, although it isn’t impossible for enderians to live past 200, it is unheard of for an enderian to live longer than 300 years.