Kong is Garp and Sengoku’s senior, yet he’s still busting his ass working as the Commander in Chief, a position with even more responsibilities than the Fleet Admiral, even though Garp and Sengoku have already retired. So even though he’s older than them (probably in his 80’s since Garp’s 78), he’s still actively working while those two retired two years ago. Either that or Kong is actually younger than them despite being Fleet Admiral while Sengoku was Admiral, which would mean Prime Kong > Prime Sengoku