*drags something very old from the memory*
Is
this fine for start of character concept? It's certainly need fleshing out and choice of career, but as starting concept. I'm fine with either surviving sibling as character. Sister gives a bit more range, brother of a Navy captain fit only as RT or Void Master.
Well, to expand on idea...
Kalaghans were a major noble family on not so major agriworld that doubled as supply depot for local Navy contingent. Founder of the family Gerhard Kalaghan or as he known locally Saint Kalaghan ascended to power as leader of local resistance to Chaos incursion and later leader of the Crusade that pushed them back out of held worlds. His descendants were not as famous but had solid fortune and connections with Chartist Captains, Trade Houses and Navy which allowed them to be major players in the sector politics.
Until one unfortunate day when Lord Admiral Astolphus Borclaw decided that sector (and his pride) need a short victorious war and bordering minor xeno empire was
just a perfect target. It didn't ended well neither for him nor his backers and only timely reinforcements from Black Templars that were nearby purely by chance saved sector from xeno counter-offense. In result Kalaghans lost most of their fortune and better half of the family in that debacle. Star of the Kalaghans was on sharp decline.
Seventeen generations later family manage stabilize situation and gain momentum again even if they were far from reaching their previous status. But that didn't come without cost - while old Kalaghan family were known as benevolent even if not without hiddent poisoned dagger, new Kalaghans by necessity became harsh, some may say
too harsh, even if not on the level of cutthroat feuding families of secor capitals and major hive worlds and with saving grace of being harsh on themselves first and foremost. But that also changed after a patriarch of the family lost his wife and remarried... and not for the better.
After Lord Inquisitor Arghail of Ordo Hereticus finished purge of the chaos cult that put it's clutches on Kalaghans (and third of the rest of planetary nobility and many of they contacts in the sector) the only ones that were left were Gerhard and Annet Kalaghan, children of family traitor patriarch...
Gerhard Kalaghan, Inquisitorial Agent and former captain of Navy cruiser Indominable Will
Before
incident - young but successful Navy captain with great career ahead. After - object of constant suspicion for what happened with his family even if he was one that brought that to light (though not by his superior Lord Inquisitor Cassius Arghail of Ordo Xenos). Always strict and reserved, though now there is a deep cold rage for all things Chaos and traitors beneath cold exterior. Loves his sister dearly though that shouldn't come unless other sibling would be NPC.
If chosen I see him in two variants - either older version as Rogue Trader that gained chance to restore his family in the service of Lord Inquisitor, or younger version as Void Master that doubles as (un)official Inquisitorial representative on this venture.
Annet Kalaghan
10 years old at the time of incident Annet spent her earlier years after that aboard of Inquisitorial Light Cruiser "His Punishing Light" that acted as mobile headquarter for Lord Inquisitor and which her brother was captain of. After that I'm not sure about her story and it can be molded for what needed if she's chosen. Personality is a bit in flux because of that too - only constant thing being idolization of her brother.
While she obviously have ties with Inquisition it's not necessary as close as her brothers. If she stayed on Light with brother the she is like with her brother (un)official representative on the mission as...
Senechal - she stayed as scribe and later investigator, meaning that there is a bit (or actually much) of fake face going on. Probably most cynical version.
Void Master - apprenticed under her brother she would turn in model officer. Strict, blunt, secretly nice.
If not then either Gerhard either used his connections or asked Lord Inquisitor to settle her somewhere.
Void Master - Navy career. Still strict, still blunt, not at all nice and very, very good duelist - because of reasons that should be obvious.
Senechal - settled on some planet as noble scion, got education, "walked in the right circles"... not as cynical and jaded as inquisitorial version of the career, but much more of a snake
While other careers are possible for character, but I don't want to play that versions of her, Senechal or Void Master.
Maybe ArchMilitant.
PS. Well, or Lord Inquisitor just dropped pair "out of sight" on his contact that would be RT... but it only works as pair with Annet being 10 years old little girl NPC (that still a very good shot with laspistols, lol) and Gerhard is Void Master that still didn't dealt with his trauma.