I believe this is Isaac Asimov's The Stars, Like Dust which was serialised in Galaxy Science Fiction in January - March 1951 and published as a novel in 1951. It is considered to be part of the Empire series (although it is set before the Galactic Empire was founded). It features the a character called Sander Jonti who is eventually revealed to be the Autarch of Lingane.
Biron Farrell was young and naïve, but he was growing up fast. A radiation bomb planted in his dorm room changed him from an innocent student at the University of Earth to a marked man, fleeing desperately from an unknown assassin.
He soon discovers that, many light-years away, his father, the highly respected Rancher of Widemos, has been murdered. Stunned, grief-stricken, and outraged, Biron is determined to uncover the reasons behind his father's death, and becomes entangled in an intricate saga of rebellion, political intrigue, and espionage.
The mystery takes him deep into space where he finds himself in a relentless struggle with the power-mad despots of Tyrann. Now it is not just a case of life or death for Biron, but a question of freedom for the galaxy….
Plot summary from Amazon.com