User blog comment:Gourgeist/Shingeki no Kyojin Chapter 64 Review: Welcome Party/@comment-199.79.169.163-20141213180008

I'm theorizing that Kenny's dream is to to usurp Rod and become king. I think his dream is also the reason the Ackermans were persecuted. They tried to overthrow the King, failed, and were hunted down. Mikasa's father got away and so did Kenny. He lived for years in the underground, pursued by the MP. He met and trained Levi (who I assume is also a blood Ackerman but not Kenny's son, maybe a cousin's son) for a while before leaving (or got captured). He offered to "serve" the Reiss family in exchange for his life. Rod agreed because Ackermans are valuable (I'm betting the Ackerman abilities are known to Rod)