Akira Toriyama always meant for Vegeta to be younger than Goku, and this makes sense when comparing their power levels.

Vegeta’s Super Saiyan 3 power-up in Dragon Ball DAIMA, known as Ultra Vegeta 1, is already more powerful than the majority of DBZ.

He did it for the first time in the franchise a few episodes ago, but as a kid. Fans shared scenes of the episode on social media as it aired in Japan: Can Vegeta Turn Into SSJ4 in Episode 20?