This one's wide open, really. Basically the only thing set in stone is that the McKennas are a long line of farmers, and most likely at multiple points along their family's existence, turned to the Republic for farmer-grants and whatnot to make ends meet when harvest was bad. The Dome grows things, but not near so well as in the Tiernan Meadows, not that anybody knows that, but basically you can't just throw some seeds outside and have them grow. Doesn't work like that in reality, doesn't work like that here either xD It's a lot of work to have a farm in the Dome, tl;dr.
Anyway, Lucius has parents, probably, he himself is 39, so they're probably 60-ish, if not older, and he is the oldest of four, so he has three younger siblings. Nothing about these siblings is set in stone. I don't even have genders picked out. The only really solid thing is that they aren't farmers and have all moved away. The parents retired to a beachfront property in Eridanus. (Courtesy the Republic; which is actually very kindly to its farmers. Probably the only smart thing the Republic does. xD)
We've got scientists, handlers, general Republic personnel, we've got psychiatrists, there's a Black Market, some stuff in the Outlands, even, so really, almost any kind of character you're looking for, Imperion might be able to accommodate. There's also a small cluster of scientists trying to find an alternative to Euphoria, the drug that keeps part-bloods and Losrians from overusing their powers and killing themselves, but the fun story is actually that most don't need it and the Republic's been lying so that'll be a fun discovery. Lucius is actually into some relatively dangerous stuff, and may end up getting killed by the Republic for treason, so that's also fun.
Anyway, basically I just want siblings for my dork. Lol His PB is Chris Pratt, so his siblings should look something like him. c:
Fortunately this one has more of an actual solid direction! LOL So one of Lucius' farmer-neighbours down the road a ways often helps him cater for festivals, and they got together one day and decided to open a soup-kitchen in Pyxis. Now, because of the presence of the HoloArena's fighting rings in Pyxis and how far away it is from Eridanus (thus the less effective at enforcing laws the Republic is in Pyxis, it helps the only ranking Republic officer in Pyxis adopted it and he's the current HoloArena champion, anyway), there's a really high concentration of impoverished, mostly unregistered, citizens in Pyxis. Like well over half the populace is poor, and if they aren't in the Arena, they're criminals. Just kind of how it works.
This means, most of them really are very concerned about when they're going to eat next, and Lucius and this neighbour opening a soup-kitchen was a massive boon. It was like the most important need is taken care of and now many of these people can think about other things, so they're doing massive amounts of good, and are probably somewhat protected by Suyis' presence (he basically claimed Pyxis and no one else cares enough to fight him so here we are, he basically rules Pyxis). Suyis basically adores them for this venture and sends them foodstuff he doesn't use quite frequently.
The other details of this neighbour are all up to whomever takes them. Could even be a girl, idc.
If you're interested in either of these and want to talk about it, you can hmu on Discord! I'm really flexible a person, so I'd love to talk stuff out but I'm also not super picky and a lot of this is really loose, just a small aspect of a character, and most of the rest is really up to whomever makes them. I try to leave as much up to the ad taker as I can, because I don't like boxing people in! (I hate it, so I don't like doing it to others.)