Seri's paternal family, the Inhonores, is a long-line of pro-Federation Caldari, with a long history in the military, that were around since the first War and remained loyal. His father was a senior sergeant in the Federation Army but has since retired.
However, it is his mother, Xiuying Inhonores, that hopped on their wave of influence. She's a rear admiral, capital ship pilot in the FedNav, though naturally almost fully skilled in all things Gallentean. She came from a Saan Go family that were the administrators of a Jing Ko mining town, ruling on behalf of the Sang Do that controlled the region. Thus it makes her son Saan Go by birthright, though as a mongrel, his heritage will have him outcasted if he ever chose to pursue it.
I took the military path with Seriphyn as a Federal Marine, though the couple differences is his mother's occupation, and the fact Seriphyn was mostly a private/corporal rank, and was never an officer. Grunts thus wouldn't normally be screened for capsuleer aptitude, but thanks to the influence of his mother, she was able to pull him through. Seriphyn was the runt of the litter in terms of upholding the Inhonores family military name, as he was a youth criminal in a GalPrime Matar enclave for his adolescence, and his marine career was a five-year judicial conscription. So, him becoming a big Luminaire General has thus brought pride to his mother, who received a lot of shame beforehand.
In terms of his own power, as was discussed, there is little reason for Seriphyn to do his own "combat duties" since he has a myriad of staff to do that for him, though naturally when idle in pod he busies himself with VR combat simulations to keep himself busy. He is one of the FedNav's leading capsuleer lapdogs who does it for more than just ISK (unlike the majority of them, ie. nonRPers) and is thus awared an array of benefits from them, including the ability to influence lower-level command structures.
Moreover I imagine ranks in FDU, in terms of RP and fluff, is not totally pointless, so Seriphyn thus commands a division of non-egger personnel and staff, most of those crew his ships etc. In secret, he is one of the Black Eagles' capsuleer, though his honesty and intellectual inability has led him to just be a combat one (read, mission agent work ^^")