This is an interesting idea. If you are going to go through with it fully, I would suggest giving the player a plethora of dialogue choices with his or her family members.
This isn't just because I want you to work your butt off to make a fun mod, this is because immersion is my first priority in the mods I use. For example I am normally against the legion barbarians, so If my brother was a member of the legion (like one of your brother proposals appears to be) I would want to severely rebuke, maybe even fight with him over it.
The only verdict is vengeance, a Vendetta, held as a votive not in vain, for the value and veracity of such shall one day vindicate the vigilant and the virtuous.
Verily this vichyssoise of verbiage veers most verbose, so let me simply add that it’s my very good honor to meet you and you may call me, Archangel