For the green haired kid (Duke Rosea's son), the twins are probably less wary of him because he's still a child. Their main issue regarding trust is directed towards the adults in their lives. So Rosea's kid has the advantage, as he appears to be nothing more than your average child, and should be incapable of evil acts and being two-faced.
The twins, when confronted with other children, seem to mainly expect teasing and verbal barbs from them...but it "isn't their fault, because they're only following what their parents say"...Rosea's kid is deceptive and manipulative. He hasn't said one bad word about them or acted openly hostile in any way, so they kind of trust him.
About the emperor's conversation: Yeah, they probably heard him say that his life was being threatened, but I guess it's kind of easy to take it the wrong way without proper context of prior knowledge? Arien and Arjen probably just focused on the "contract" bit and thought that the only reason they were alive now is because the emperor *had* to let them live out of his own sense of self-preservation. For them, it's kind of confirming their suspicions that he never did, and probably still doesn't, care about them. He's only continuing to let them live because he was forced into an agreement.
They probably also don't really believe that his life was ever in any actual danger. He's meant to be the strongest man in the empire and is thought to be literally blessed by the gods, right? So who could possibly threaten his life? Definitely not Rurahel who they think was just a regular lesser noble with zero power, influence, and connection compared to the emperor. They might think he was exaggerating.
Like, instead of his actual life, he meant his *way* of life and his image in the public eye. They probably think that Rurahel tried to become the best empress by seducing him, failed but got pregnant, then blackmailed him somehow...and he, in exchange, promised to let the children and her live + gave them a small life of luxury so long as she stayed out of the way and kept them a secret (since illegitimate children are a stain in the royal name)...but who knows! We'll probably find out their thought process next chapter
The 'also hearing the emperor's life being threatened' is certainly a plot-hole, but I feel like it is probable that they genuinely just heard the end part on their way to somewhere.
I think that they're realistic in a weird way.
They're 23 and they shouldn't be acting like this. If anything, they should be smart enough to have made a moral philosophy where they know how to react to people who have wronged them, but the fact is that they act like they're genuinely five.
I like the concept, and the reaction to abuse is realistic if you think that they're five.
But the problem here is that they're not five, they're twenty-three. It doesn't make sense for twenty three year old adults to react to abuse in such a way and it doesn't make sense for twenty-three year olds to be acting and trusting people like they're five.
On the other hand, they're constantly in a life-or death situation since their father is the emperor who in their eyes, could easily kill them with a simple wave of his hand. The emperor made it worse by almost killing the one adult who would be relatively honest with them. That isn't something that fosters trust.
I genuinely want this to be good, to be as realistic as it should be, but the thing is, I doubt that they'll ever act like actual adults in the presence of anyone that they should trust according to the plot.
They said that sexy red wolf didn't make them put up their guard although he was new but yet they seem to trust the little green head bitch. Also, I'm hoping I'll be proven wrong, but at the end of this chapter when the emperor mentioned killing them, they shouldve also heard that it was a life and death situation for the emperor. They have almost 30 years of life each, why does it seem that they don't process the material that way? Abuse and what's not isnt a joking manner but it's like even after entering a different place, inclusive with the previous abuse, they aren't thinking the way I would expect them to.