There have always been 2 Princesses of Equestria. In recent years, two more have joined the Royal Family.
They rule with harmony and grace, and are loved by all Equestria. However, there once was a third with the two sisters.
And HE still lives.
Luna did not bear the stars once upon a time. That was his job. He shaped the stars into art. Into beautiful constellations that bedazzled the ponies who looked upon it.
So where did he go?