Minor nitpick: This particular subpart of Freudian psychology (like a lot of stuff he did, actually) has essentially been totally discredited. They’re pretty sure that once all these high-society women started telling him they’d been abused by their father he couldn’t bring himself to believe it, so he concluded there must be another explanation … when in fact no, they were (most likely) telling the truth.
Time to put on my Sister Princess fan hat¬Ö because I know you’re a fellow SisPri fan. 
In the relationship arena, the central core of SisPri is purity, innocence, and trust: their brother never crosses the line.
Sakuya’s advances are rebuffed by him feigning ignorance in intimate love ¬ñ playing dumb or pretending no to understand the double meanings in her actions. It’s proven to be frustrating for her at times, but the challenge of it all (not to mention his ability to reel back in when he’s pulled too far), keeps her from giving up hope.
Chikage advances are stopped by his true purity. Because her divinations reveal she and he share two halves of the same soul, and Chikage is certain her part of the soul is tainted with darkness, he has proven that no matter how dark or corrupt Chikage might become, his purity of the other half ensures she can always return to the light. Therefore whenever she makes moves that might corrupt the purity in her brother, she refrains. If he is to corrupt himself, she wants it to be of his own freewill… yet she seems to be aware that such an event may never come. Which only causes her to love him more so: he’s incorruptible. Everything which she is not.
As for the other sisters… while the bulk of them are too young for incestuous thoughts, it seems fairly inevitable they will face that challenge nonetheless. They will grow up one day ¬ñ just like Chikage and Sakuya did ¬ñ and then realize their admiration is difficult to separate from intimacy. Their brother is the perfect man: he would make a WONDERFUL husband and father. The problem is that he’s their brother. Furthermore innocence doesn’t mean they’re oblivious to incest. Look at Karen and Haruka: both are aware it’s culturally and religiously forbidden to marry their brother - yet they still desire it. Karen is quite aware of the implications, but outright ignores them as irrelevant. She loves her brother more than ANYONE in the world. In fact, Karen’s obsession is more frightening than Chikage’s and Sakuya’s ¬ñ she truly believes her brother can commit no wrong and that even his mistakes are miracles in disguise. Haruka knows what the duties of a wife are, and when she thinks on them deeply, she goes into her classic “poh, poh, poh” fantasy mode. It’s quite obvious she KNOWS of sexual activity ¬ñ when speaking of romance, the idea of kissing and hugging throws her into a momentary daze out of reality. Haruka ¬ñ as a Yamato Nadeshiko ¬ñ doesn’t speak about this aloud… but it’s not a sign of ignorance. Also it can be easily argued that Mamoru and Rinrin, are slowly becoming aware of their feelings being more than sisterly. Maybe in a year or two, they’ll be at the same level as the elder four. Yotsuba blushes at the prospect of doing a “checky” on her brother’s dresser (and what he sleeps in)¬Ö which may or may not be a sign of her own growing awareness.
SisPri comes off as a harem, because the sisters collectively only want one man in their life: Onii-chan. It’s not the traditional harem… and SisPri isn’t a model that all harems follow (that’s what makes it so neat), but the mentality of the girls wanting the same man - ignoring all other men in the process - is harem-ish. I think a baseline has been established, that each sister will undergo a trail in which she has to deeply examine her relationship with the brother on a romantic level. How she reacts to the decision, obviously will vary, but his will always be the same.
He is their loving brother: and it will always remain so no matter what.
Of course if it turns out he isn’t blood related… woot to the max! 
Oh, I’m pretty sure Sakuya knows her romantic feelings shan’t ever be returned, as it was (beautifully) implied in the RePure episode dedicated to her.
I think Chikage is also able to endure it because she has the conviction their souls are bound for the whole eternity, so she can afford to wait for another life. She knows that they shall be reborn, and be able to meet again in their next lives.
Well, to Karen, her brother is Superman after all (and, to be honest, the game’s character seems to indeed be someone deserving praises for being rather athletic, kind, protective, clever, a good student, etc.), but I’d say that put her in a her own category, with her feelings closer to worship than romantic love.
As for the others, it may be me, but I see it as way more innocuous (and innocent) sibling love than anything else.
I’m not too sure about how the girls’ (especially the youngest --Aria and Hina) behaviour could be constructed as “only want(ing) one man in their life” since they feel more like merely missing their dear brother they only meet once a while (this feeling is especially apparent in their drama, I’d say), but I guess I can understand your point. I don’t agree with it, though. I think a trial would merely be for them to live together for some time, instead of separately (though, with their parents overseas, I can understand the logic behind putting the girls under the care of relatives). Of course, you can argue that it used to be the case (IIRC, it was before Hina was born and before Marie was hospitalized, leaving Sakuya, Chikage, Rinrin, Mamoru, Marie, Karen, Shirayuki and Kaho) but I’d say they were way younger back then so things were pretty different, with her brother being the elder and only boy (therefore the “man” in the bunch).
Someone just pointed out to me that Nozomu not showing open attraction for his students, is possibly a sign he cares for them. His sister constantly points out, that the Despair Sensei is a womanizer (or at least has sex all the time)… kinda disturbing that she’s so detailed aware of this… but then, that’s the point.
However he repulses any advances from his students… not for lack of attraction either (he noted Kiri was beautiful for example; and thought Matoi was cute when she dressed like him). Probably doesn’t love them sexually… but he respects them. He does show attraction for the “College Girl Next Door” (Kafuka in disguise)… maybe he’s just into older women. I think he’s too afraid of Chie to notice her killer body.
nice parodies in those attachments. Especially the bottom one of Despair Sensei. Reminds me of Laharl and I was expecting an Etna or, probably more appropriately to how she acts, a Flanne paradoy of Kafuka.
As for the assesement it is sound, but then would he have thought differently about Kafuka as the “College Girl Next Door” if she was a “High School Next Door”?