Vargr:
As prestige is so key to Vargr leadership, they can rarely or never make strict primogeniture (or gender divsion) work for them in the long term. What normally happens is that the offspring of the noble in question compete against each other to be named as 1st Son, 2nd Son, and so on. This character would be one of the sons of a Vargr leader enobled for his part in, more or less, peacfully keeping a strategically important and highpopulation but midtech Vargr world as an Imperial Client state.
Said son has decided to seek his fortune in Imperial Service, probably the Navy - though that service choice is dependent on the rest of the PCs. This is made rather more difficult by the fact that not only he is from a backward and barbarian planet, he's from a race reknowned as honourless and
Human:
Only son from a very old noble family that has only recently recovered it's fortunes, until recently they had little but their lineage and an august history to their name. This is partially because their fortune has since suffered from a long line of dissipated wastrels, so much so that their house is nigh-provebial for it. It is also because of some bad investment decisions. The fact they conspiciously do not follow mainstram Imperial religion counts against them to.
Their holdings had essentially shrunk to a significant chunk of a frontier ranching world, where they dug in and sought to rebuild their fortune, in recent decades having become significant figures in the planetary milita. The family's renaissance began when their world was invaded, the resident "Old Noble" family were upstarts compared to his line, but they were much richer and in favour at Court. However they badly botched the defence of the planet, being either cowardly, incompetant or traitorous. At least one scion managed to be all three at the same time, fortunatly he did more damage to the opposition than the Imperials.
It was left to the characters father to organise resitance and boot out the invaders. This was duely noted by the Emperor who promptly elevated him to Governer of the planet as well as a couple of its neighbours and gave him a fair chunk of the old noble's fiefs as well. While the PC should be learning at his fathers side, family tradition dictates that he pursue a military career first. It will also help him make friends and allies they sorely need, however it also brings him into contact with several people with a grudge, be it relatives of the "Old Noble" family he supplanted or various miscellaneous nobles who remember how his, Great, Great, Great, Great, Great, Great, Great, Great, Great, Great, Great, Great (etc) Uncle Horace debauched their Great, Great, Great, Great, Great, Great, Great, Great, Great, Great, Great (etc) Aunt Hortense and are burning for vengence.