Solaria/Comics

Pre-Comics
As revealed by Former Queen Luna in An Unforgettable Party, Radius grew up with Celsius, his half-brother, as if the two were related wholly by blood. Somewhere along the way, however, Celsius believed himself to be a more fitting ruler for Solaria in comparison to Radius, who was set to become the next King of Solaria. This caused a major fight within the royal family until Celsius, frustrated and enraged, abandoned Solaria as Radius continued to be raised to succeed the throne.

His defection from the royal family occurred long before the birth of Princess Stella.

Season 4

 * Issue 97: The Dark Dimension

Season 6

 * Issue 130: An Unforgettable Party

Season 7

 * Issue 150: Magical Sparkles