The Hydrogen brothers Protium, Deuterium and Tritium were all of the same H, but quite different at heart.

Protium was quite the common type, whereas Deuterium felt special, claiming he’d been around since the beginning of time.

Tritium though - he just couldn’t help it - was so radiant that others often steered clear of him. For the next twelve years, he would spend half his life decaying on his own.