In the wake of Darktow I am once again thinking about the Dwendalian family, specifically with respect to Caleb. Rather than actually breaking free from Volstrucker conditioning, which frames family as an effectively Volstrucker-Empire concept, Caleb tries to reenact an idealized version of the family through the Brenattos. This leads to him being upset and uneasy whenever that structure is threatened - especially by his own potential inclusion and Veth’s attempts to not be defined solely in the “mother” role.
The rhetoric of the Volstrucker - and of Ikithon - is based around the Dwendalian nuclear family as the correct and integral unit of society, phrased most clearly by Astrid in c2e89:
But I also know the reason that we get to sleep, every night, in a comfortable inn bed, or in a manor, as do the many families and children just like we were, just like the families we once had that don't have to make the choices we did. They still get to live, happily and comfortably, because the few, the chosen few, made the hard choice, and do what few have the will to do.
The nuclear family is framed as the natural unit of society: mother, father, their children.* The Volstrucker, in order to become Volstrucker, must cut themselves out of their family units (quite literally) and become the "chosen few," forever isolated from those structures in order to protect them; and they do so specifically to protect and reify those structures.
They do it in order to serve Civil Influence - and we know that the role of Civil Influence is to stabilize Dwendalian society, keep down rebellion, and protect the Crown and Assembly from populist uprisings. They kill traitors, but they also enact this through the rhetoric of the nuclear family. "Do you have the strength to protect your homes? Your families? Your country?" (See Caleb's Origins comic.) Ikithon frames the Volstrucker as a barrier between "civilization and chaos" in the same breath that he invokes the family as the base unit of that civilization. It is their will that preserves the country through preserving the family: even as they destroy their own to better serve. They don't have their own nuclear families anymore, so they spend the rest of their lives enforcing that structure on the people of the Empire.
Their function is to reinforce the very unit that they are forbidden access to. It positions Volstrucker as individually worthless (because they cannot participate) but societally necessary for the continuation of the Empire - in its base unit formed around the nuclear family. The family is the Empire, in microcosm.
And yes, Caleb leaves, helps tear Ikithon down. But he never gets rid of that construct of society and of his role in it in his head. He's done something - he's part of a (damned) chosen few - who can and will never be able to participate in society because it is structured around family; and, having murdered his own, he acts as though he is obligated to protect the nuclear families of others.
Specifically? Veth Brenatto's.
I'm eliding a lot here. There's great meta on the topic. Suffice to say, Caleb is obviously and repeatedly torn between wanting Veth to stay with him and protecting her nuclear family of her, Yeza, and Luc throughout the campaign and post-campaign. Liam has said this is at least in part due to seeing Luc as like a younger Caleb/Bren ("that's me, that's a little boy in the Empire" - Talks Machina 157); he acts as though, by keeping Luc's family together, he can rehabilitate his own relationship with his broken, dead family.
So we come to the Brenattos in Darktow - and specifically, his automatic rejection of Veth including him as a parent, even jokingly, when speaking about her new son Bren-Bren. She jokes that he's like a first time parent, and then amends to STEP-parent. It's Caleb who cuts her off and offers godfather in exchange. A stepparent is a parent - having one would mean Bren-Bren has three parents, who are at the time of writing living together and sharing full-time care for a child. A godfather is a trusted outsider to the family unit - and the person a child would go to, if their parents were both to die.
Caleb rejects the label that would imply any kind of aberrant nuclear family structure: no additional parents, no marrying in, no significance beyond "teacher" or "godfather." Even if he is acting as a parent, he cannot be one - in the same way that, despite his clear desire to remain with Veth, he gives up and resolves to content himself with the "memory of being partners at a certain time of [his] life." (Beau, c2e68). But he also won't leave! He can't detach himself from the family, but he also can't allow himself to be a part of it. It remains incredibly significant to him, while being forever and definitionally beyond his reach - because to accept that label would mean both integration into a fold he believes he has lost the right to access, AND it would destroy the image of Veth's nuclear family (mama, papa, son, baby. No wizard; no third parent; no Volstrucker).** Even when she's the one who offers.
He also panics over the idea that Veth might disrupt the structure of her family herself. Veth struggles with this herself - her persistent desire to adventure, steal, and otherwise cause chaos is strongly at odds with the obligation she feels to her family.*** In the Darktow show, when she expresses a desire to adventure, he asks if she's sure, because "a boy needs his mother - Bren-Bren needs his mother in his life." He wants Veth with him; but he can't stop objecting to her joining him because of the danger it would put her in, and thus specifically her child at risk of growing up without her. The perceived risk is of the disruption of the family that he actively cares for and tries to protect just as much as it is to Veth's own life. Caleb regards her as a dear friend and a life partner, and respects her choices - but he also can't quite shake that her role in the nuclear family is "mother," and his own complicated beliefs tied up in that.
And to add to all that, Veth named the kid after the version of Caleb he believes in as an innocent child. Surely that won’t cause any more problems.
tl:dr: Caleb defines himself out of nuclear family structures (specifically: the Brenattos') while simultaneously holding them up as both meaningful and idealized due to the indoctrination around "family" he received as a youth equating it to the basic unit of societal good. Rather than break the conditioning, his guilt causes him to try and re-enact a "healthy" version of a structure that does not benefit the people who live within it.