User blog comment:Xilinoc/Ch. 549 - The Stormbringer/@comment-4620155-20130917204342/@comment-11051098-20130918173656

Regarding Kisuke, he might have become the 3rd seat while he was still weaker than Marenoshin, but then worked his way up, improving his skills in combat as well as achieving Bankai, and become the stronger one while still being the 3rd seat. We don't know how many years Marenoshin was the lieutenant, and Kisuke the 3rd seat.

But seeing how Kisuke was promoted to captain, and Marenoshin remained lieutenant, I'd say either Kisuke became the stronger, or Marenoshin was equally strong, but didn't have the qualifications to become captain.

But it would indeed be funny to see Marenoshin come out of the dark to help his son, if he still has his Zanpakutô and is able to fight.