Z (LOTSG)

"Oh... he's my dad!"

- Prime Zero to the Z-Warriors about how he knows Kaestos Zero, sometimes referred to as Prime Zero, is the Prime Universe's version of Zero and the adopted son of Allie and Kaestos.

Personality
Prime Zero is entirely different from his alternate counterpart, instead of being a murdering and sadistic tyrant this Zero is a honorable, good person.

Zero's relationship with his parents is a good one, respecting both of them for helping him become who he is, however he finds Kaestos to be easier to connect with than Allie, despite loving his mother just as much as his father.

Background
Zero was born on Planet Freeze, unlike his counterpart, and was born to a royal lineage among his people. During the coup d'etat by the Cold family Zero was hidden away by his parents, miraculously he was never found during the event.

After the Cold Family destroyed his families palace Zero was discovered and placed in an orphanage, his identity was discovered shortly thereafter but he was viewed as a non-threat by the Cold Family.

One day, perfomring his duties as a Honorary Supreme Kai, Kaestos came across the planet Zero was being cared for on. He soon discovered that Zero was on the planet and planned to destroy what he believed was the same twisted being he fought in his universe, however upon seeing the innocent child Kaestos couldn't hope to harm him and with Allie they instead adopted the young Frost Demon.

For years he was raised by the two and came to love them as his own parents, and they in turn loved him as their own son.

One day Zero discovered that he was the counterpart of the monster that slaughtered the Z-Warriors of Kaestos' universe, this discovery left him in shock as he was unable to comprehend why his father didn't destroy him at first sight.

When Zero asked his father if he even thought of destroying him Kaestos admitted that he had, but only once. When he heard that Zero was on the same planet he himself was on the only goal on his mind was finding and killing him, but after looking on the innocent and orphaned child he couldn't even think of killing him, the only thought on his mind was to help the child and from there he adopted Zero as his own.

Kaestos admitted that at first he saw the evil Zero from his universe when looking at the growing Frost Demon, but for years he had only seen his son, not the monster from another universe.

Eventually Kaestos sensed a few incredible powers coming from the Prime Universe's Dragonworld and went to investigate, for the next 10 years he would spend time between Dragonworld and his home, raising and training with Zero and training with the Z-Warriors at different times.

During the conflict against Buu Zero wished to join in the fight, however his power was less than that of Super Saiyan 2 Goku or Vegeta. While he initially desired to take part in the fight after Majin Vegeta was beaten into submission by the monster Kaestos forbid him from joining the fight, with Zero not willing to argue against his father.

During the time between Kid Buu's defeat and the tournament between Champa and Beerus over the fate of Earth, Zero had gained a great deal of power and was on par with Final Form Frost

Power
Like his counterpart Zero had incredible power as a child, but unlike the alternate Zero this one was almost killed when the Cold family took over the Frost Demon race during their coup d'etat, which didn't happen in Kaestos' universe.

After being taken in by Kaestos and Allie Zero was taught morality and then was trained by his adopted father, and then trained on his own.

By the time of Buu's return Zero was weaker than Super Saiyan 2 Goku or Vegeta, and had no qualm about staying out of the conflict after he witnessed Majin Buu brutally beat Majin Vegeta into submission.

By the time he turned 16, during Champa and Beerus' tournament, Zero had gained a great deal of power and was only slightly weaker than Final Form Frost and Ultimate Super Saiyan Gohan. Kaestos demonstrated pride when Zero demonstrated his power in a sneak attack on his father, commending his son for becoming so strong.