I have only just finished Stormblood.

However, I can't help but feel that Pipin has risen through the ranks due to nepotism. He doesn't really seem to be that talented, and yet he is being given a LOT of leeway in the planning of battles.

However, he is then promptly promoted to guard the Sultana (I assume he and the Sultana are in a relationship, based on the last scene I saw of them)

Perhaps nepotism is explored a little bit later on.