Okay Kingfisher lets start at the Beginning:
Im not sure if we play here strictly historical or not, in case we do women in the senate are propably not working out. Although i might be wrong.
Starting out as the son of a Senator is ok....just cut that crap with running away, parents getting killed by somebody and swearing revenge to anybody. How many people do you know in RL who ran away from their parents, never returned and then ended up in a high military/political position or whose parents were killed by burglars/gang-wars/criminals? Take that number (which should be ranging between zero and 1),multiply it by 10 and you have the number of such happenings among a billion.
You see what i'm getting at? The child whose parents were murdered by bandits or ran away from home and fights its way to the top is not the rule but the exemption. If you really want bad relations/dead parents try a different approach something less "HAHA i'm the Caricature of the Fairy Tale Hero".
If its military why not try to have a Middle-Class Family with a drunkard father? Your Character joined the Military to escape his father, the social standing of you allows an entrance as a Decurio and thus maybe a high enough position to lead regiments before you are 50. Let the Character have a ambivalent relationship with his father: when he is drunk he is a disgusting piece of shit and when he is normal he is actually a loving father. There enoughs tuff for roleplay...
If its senate position, why not play mama's boy? You come from a Senate Family, your father was adultering and you witnessed as your mother killed him and blamed a slave in very young years. Now your mother has been grooming you for yours to take the Senate Position of your father. Gives a nice interesting character with some comedic relief or you make him some real psychotic guy.
There are a trillion different life-stories of people out there than ye olde: my parents got murdered by bandits thing. Go wikipedia skim over some biographies of people in charge: most of them have actually really interesting stories (none of which start with he ran away from home and never came back). Develop a quirky unique Character or a bland normal one, if you are not in the mood for that. Just not a Mary-Sue. Read the Bios and posts of Terenos (especially thinking of Terenos D'Avistral from YAK here) or of Yoink ( Troubaldsome) to get a feeling for badass or really awesomely crazy characters if you feel ambitious or read Dwarmins (Aeverys,Albert in HOTRS/YAK) or one of the myriad others of good characters in the forum(Caesar,Iituem,forsaken1111 etc. pp.). Try to get a feel how these people write their Characters and how they play them, if you can't really can come up with a good backstory or some ridiculously crazy character just try and make a normal one. Play yourself more or less or take somebody from your direct vicinity (friends family). Take their Character and/or their looks as basic build and from there on out you can change everything at that character. Or if thats not working out just make a blank, in other words some random people Character. The backstory at the beginning is not so important you can flesh out your character in the game itself. I usually do this as i seldomly can come up with a good character on the spot.
If we take for example Shebs character here (sorry i hope you dont mind):
Appearance: Tall and thin, with a wisp of dark curlay hair around his balding head, Lucius is still in a remarkable good shape for a man of over 45. Born from a wealthy and ancient patrician family, he was destined for public office from birth. A skilled general, he led a succesfull campaign against the Whitepeak alliance before coming back to serve in the Senate as one of the Optimates's most influencial members.
Its wonderfully vague and specific at the same time. Betraying nothing of his character sheb can form this guy into anything he is in the mood for: drunkard, coward, whoring bastard, pedophile or a loving father, a good soldier, a skilled politician, a savvy schemer, a loyal ally. The man could be dreary, he could be cheerful, he could be anything actually.
At the same time even if we don't know the character we can figure out what he looks like and that he was groomed to be a politician/general from birth. That gives sheb enormous leeway to put childhood traumas there if he wants, or make his character especially ambitious.
Well you hopefully get the idea. I hope that was somewhat helpful and i hope i didn't sound like a jerk. The basic point is: be creative or be bland. But don't take the Mary-Sue way...thats something nobody except for yourself likes.