Sorry, been a bit busy.
I'll flip-flop and go with the Human if that is allright:
Dominic hault-Propenser
The hault-Propenser's are an old, old family. Back in the dim and distant past they were some of the greatest nobles in the Imperium, however they were always a very military family and gave compartively little attention to politics and business. This lay the seeds for their undoing, after a few hundred years their members became much more "conventional nobles" - however they lacked the accumulated contacts, wealth and resources of the less martial clans and found themselves drawn into to expenditure they couldn't really afford in order to keep up with them.
It wasn't helped by the downright decadent actions of some of line, who along the way forgot that the spending lots of money on lavish entertainments, big estates and private yachts is a means to and end rather than an end in itself. To this day the hault-Propenser name is synonmous with rakish wastrels, uncultured boorish behaviours and an obstinate refusal to adhere to mainstream Imperial relgion.
Estates and titles were gradually lost, their main capital was thier good name and illustrious reputation and that was all but gone too. With what remained a far sighted patriarch sponsored a major exploration and colonial expedition to discover and settle new planets, with this the hault-Propensers disappeared off the radar of mainstream Imperial history.
Though they didn't find too many planets they did find and claim a small cluster of 4 frontier worlds: Gasper, Trillian, Entberg and uU. Here they settled down and sought to rebuild their shattered fortunes. However once again their lack of standing at court hurt them, as a later Emperor decided to strip them of the Baronial title to the cluster and grant it to his current favourites. Embittered by this further loss, the Hault-Propensers withdrew to their own estates mostly spending their time in quiet ranching on Gasper when they weren't involved in running the planetary miliita.
The family's renaissance began when their world was invaded by, 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 Dominic's father Aetius to organise resitance and boot out the invaders. This was duely noted by the Emperor who promptly reversed his predecessars decision, elevated him to Governer of the planet as well as Count of the cluster and gave him a fair chunk of the old noble's fiefs as well.
While Dominic 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. It also doesn't help that Count Aetius is a little bit overpromoted and the Family are generally unready for their new role. This makes them a bit provincial and everyone is waiting for them to screw up again.
Well almost everyone, some aren't willing to wait.