My own 2-cents. 17 and he's lieutenant, sounds too good to be true. I'd understand if he was prince, but he's only Irohs adoptive kid. And being adopted in strict monarchies, he wouldn't usually be treated on equal standards as those of the bloodline.

Edit, you already addressed the lineage issue, but to be a lieutenant at 17 is still out there. In my own opinion though. Whatever Prince deems fine is his business