His parents are Vopiscus Essair and Ksenia Essair (nee Warwicke).
Cyprian is his elder half-brother from his mother's side.
Kassandros and Icarus are his elder triplets.
Born the youngest of triplets, Kassandros first, Icarus second, and then Cygnus, to say the least of it, Cygnus was somewhat coddled and at times, almost forgotten. You'd presume, of course, that the occasional penchant for everyone else to forget, at least momentarily, that Cygnus existed too, in light of everything his eldest brother was capable of and knew, he'd have turned out much different. Cygnus, however, ended up more or less left to his own general devices. He got up to, and into, whatever it was he fancied, and when his mother, short-lived though her presence may have been, or father happened to remember he did exist, he was often coddled and somewhat bribed into being still.
The problem, of course, was that what Kassandros and Icarus lacked in energy levels, Cygnus inherited, instead. The boy never held still, rarely ever stayed in one place long, and when he wasn't pestering his family, he was bothering the slaves, talking the ear off anyone that would listen, and this penchant never really stopped. Cygnus has always needed stimulation, not just physical or mental, but both, typically in conjunction with one another, for it to really be effective. His inability to really hold still and focus on anything, coupled with the fact Kassandros was always clearlyworlds beyond him and his meager capabilities, to say the least, it left behind some, how you say, insecurities and perhaps resentments.
Cygnus, after their mother decided to ditch House Essair (which, Cygnus blames entirely on Kassandros and his goddamn being special), spent perhaps too long effectively warring with Kassandros for their father's attention, but, Kassandros was oldest. By maybe ten minutes, but he was still the oldest, and Cygnus was the backup for the backup. Naturally, he barely registered in their father's mind, hardly managed to keep his attention very long, and when he did, it was empty, senseless placating, rather than anything real and solid. Incidentally, Kassandros, Icarus, and Merenwen were the only ones that ever really gave him the attention he so desperately sought, and when he'd decided that wasn't enough, Cygnus decided the rest of Dalmasca would give him what he was looking for.
He's made many friends. But he is a nonstop word machine, and it takes a special person to be capable of putting up with his immaturity, his motor mouth, his habit of swapping randomly between being twenty something, mentally, to being perhaps twelve. Essentially, though, Cygnus just craves attention, far more than he should, and instead of accepting that he gets it now, he's always looking for more of it. He could easily fall in with the wrong people, if said wrong people could stand him, and of course, Kassandros and Icarus are always going around behind him, cleaning up his messes, destroying whatever might hurt him first before he's even aware it's there. He is, perhaps, perpetually just a six year old kid that wants someone to pay attention to him, and the nuances between good attention and bad never quite registered. He still resents Kassandros, perhaps even more so, now that he's decided he wants Imperator (doesn't that asshole have enough?), and tends to ignore him, even now that he's head of house. Maybe especially now that he's head of house, because frankly, Cygnus has no reason to listen to anything Kass says.
Or Icarus, to be honest, but he's at least more open to listening to Icarus.
Bitterness, more than anything, eventually drove him to joining the military; he doesn't hate his brother, but, perhaps some finer details of courtesy and respect got lost, somewhere between trying to find who the fuck he even is, and being happy with who that is, amid living in Kassandros' shadow, but the funny thing is, he dwarfs Kassandros when he's in the vicinity of him. Cygnus is a big personality, the kind of big Kassandros never could be, and unlike Kassandros, Cygnus has all of the emotions of the bunch (probably even a good deal of Icarus'). He's emotionally fragile, very easy to manipulate, probably too trusting, and if it wasn't for his brothers, he'd probably be dead by now.
Even in realizing this, he still finds some bitterness to aim at them both.
He's learning. He's made a lot of mistakes and is now trying to fix them, but you can't really repair things overnight, it's a hard lesson to learn, too.
Cygnus is schizophrenic. What this means is, his critical thinking and cognitive functions are notably impacted, by way of disordered thinking and inability to make sense of anything. He's incapable of making the logical jumps for... almost anything, he takes everything at face-value, basically. He also cannot focus very well, his attention span is about two centimeters long, and he does not understand unspoken social cues or body language, non-verbal gestures, or facial expressions. They just don't make sense.
At times, his verbal communication probably kind of shuts down, and he doesn't make any sense, either.
He is not purposefully vicious, but he is very, very impulsive, and he does and says things without thinking, because essentially it's so hard for him to think straight, that he simply doesn't.
He may have hallucinations, occasionally.