Hiruzen...this man protected him as a child and hide the truth about his family and brother...Hashirama will tell him about the early days of his clan and Madara and Minato about tobi and the kuuybi. But Sasuke is main quesstion is about his family.
I think the second hokage,tobirama senju,will impact him the most.the second was responsible for making the police force as an act of oppresion against the uchiha
OK but Minato wasn't related to none of the Hokage's. Jiraiya was the better one for the job sorry. Yes it does mean a lot more that she is part Senju but you have just confirmed what I said which is "that she is nothing more than a relative now". But she definitely serves her purpose though.