Thom Kallor is the real name of Star Boy. Born on an orbiting star observatory, Tom gained the ability to draw mass from the stars and give that mass to an object, making it super-heavy. Thom later was exposed to the tail of a passing comet and gained abilities similar to Superboy. With these abilities, he applied for and was accepted into the Legion of Super-Heroes.

Star Boy served in the Legion, until he lost the powers inparted him by the comet. He was injured and spent several months recuperating. Upon returning to duty, Star Boy killed a former suitor of Dream Girl's to protect her. It was later proven by Brainiac 5 that he could have stopped the man without killing him. For this act he was kicked out of the Legion.

He served for a time with Dream Girl in the Legion of Substitute Heroes, until he was given Legion membership again. Due to the Earth being surrounded by a cloud of Kryptonite gas, Superboy and Supergirl were forced to resign. They nominated Dream Girl disguised as Miss Terious and Star Boy disguised as Sir Prize to take their places. The two former Legionaires distinguished themselves and were later accepted again under their own names.

Star Boy has resigned from the Legion when Xanthu, his home planet called him back to act as the planet's protector, after Atmos, the planet's former protector, disappeared. Atmos had been kidnapped by Universo and even after he was freed has not returned to Xanthu, leaving Star Boy as the planets protector.

Star Boy has been romantically involved with Dream Girl.