It's about fu*king time. Just as I and many others stated last week Aizen knows Isshin.
Ichigo gets shaken up by Aizen's speech
Furthermore, Aizen tells Ichigo that the focus of his own quest was for Ichigo's growth,
from the meeting with Rukia and sudden attack from a hollow, the menos appearing for the quincy's scattered bait,
finding Rukia in the living world, and being reported to SS,
fighting with Shinigami captains in SS and everyone else, forcing Ichigo's power to rise,
didn't he think it was strange? - so says Aizen to Ichigo while stopping his slashes with a hand.
and all the while Aizen is still unharmed, "Isn't it the truth that I know everything about you?" He asks Ichigo.
From Rukia staying in the living work out of duty, who do you think,
gave Renji the Reiatsu detection equipment to seek her out, who do you think,
gave the vice-captains the report about Ichigo and co.'s progress and other information, who do you think,
besides me, who could after all, have over a 100 years confirmed the whereabouts of the hougyoku?
And after all that he asks Ichigo whether he has the confidence to say that he knows it all perfectly
Aizen has, from the beginning, since he had been born, has something to return to him.
You've been special the moment you were born, especially why you are a shinigami-
and at this point, Isshin comes, and then it's on to next week.