Star Saber Junior or just Junior is a blade formed from three Microns; Saber Ichiro, Saber Jiro, Saber Saburo, who are all sons of Star Saber born from the...failed relationship with the woman he loved Makoto Kenzaki.
Thankfully for her, Shining reset the events of that night and add some change to prevent the attack on her.
Those kid were born from the first timeline, saved by Shining because of his merciful nature. They exist outside the timeline and existence itself, so no one can remove them from existence.
As they were technically born in a timeline that no longer exists, only Star Saber knows who they truly is due to Saber having difficulties with explaining their origin to Shinning Convoy.
After the Retcon, they served as Star Saber's replacement for his subpar Saber Blade
- They're base on the Armada Star Saber.