Hmmm, the 'lieutenant' could be a favored 'whipping boy' of the eldest prince [Who i'm going to be making once there's a CS and more details to work with] =3 that is to say, someone he 'spars with' on occasion and seems to use to show off, but ultimately is just 'maintaining his princely demeanor' while helping to nurture a guard showing potential over the rest, even he does so in a way that hurts... he wouldn't be the only one of course, just, so far, the only one controlled by a player XD
To be more specific, full contact sparring, forcing someone into a position where they can't 'hold back because he's a prince' and allowing him to both keep himself sharp and inject a bit of more viable experience into the guard... afterall, nanny pandering around him being a prince and making it easy would just leave him a less suitable swordsman should he ever need to 'defend the realm' XD
In the same vein he understands that holding back because someone's an ally, more than is necessary to avoid crippling injury at least, would weaken the experience of the training, I see him taking the kingdom's defense very seriously, and thus the quality of it's defenders as well, even though he's not officially in charge of the guard [I don't want to take that position from someone else D:] He'd be the type to 'drop by' sometimes to see if he can enhance the training a bit. =3 Expect 'evil shiny glasses glare'!
I could see this also making him a bit of a 'scary sparring partner' because he takes it seriously, he may at some point help in giving instruction to the young queen if she ends up interested in that sort of thing... of course, in 'that' situation he would certainly hold back for the sake of learning... she'd probably just get a few bruises out of it =D
OH! OHHHH!!! IDEA! I've been considering things about magic, What if the 'public reason' this older prince turned down his succession to the throne, was because he took upon himself the 'burden' of learning magic so that 'someone' could use it to train the Kingdom's defenders in fighting someone using magic, and perhaps the potential for being 'changed' by the magic brought his suitability for the throne into question. Sure, that's 'probably' not the real reason he turned it down, but the public doesn't need to know his personal preference against having the 'chains of authority' be placed on 'himself', or that he'd rather affect the kingdom from 'behind' the king/queen while trying to make them better... oh, maybe magic 'has' changed him, made him more 'sneaky' in his methods of helping the kingdom >.> Of course, one can imagine there are others who'd be sure he's plotting something, stupid magic hating bigots =P
My brain is having fun cooking up these wild ideas!