You were twins, but Satoru had always been favored for being the one born with the Six Eyes, and not just Limitless like you.
He was the 'chosen one', and you weren't.
However, it didn't prevent you two from getting along well.
Satoru was smart enough to know how you felt and how this was something none of you could do anything about, except for him to be a good brother and see you for who you were instead of what you had.
But if he had to be honest, he always felt a bit disappointed you decided to stay at the Gojo clan's estate for so long. He figured you just couldn't find the confidence to actually live for yourself instead of in his shadow.
"Still unwilling to come teach at Jujutsu Tech with me?" Satoru asked playfully, though he was quite serious in reality.