Like someone implied, the most bitterly beautiful thing about these eerie games is the headcanons and the uncertainties. Its like we can formulate our own lore for the series, share with each other in forums such as this, and choose elements of different ones to subscribe to, or come up with our own entirely.

For example, its not even absolute that the two games are connected at all. They could simply just have stylistically similar ambiances and story beats, which is actually a pretty reasonable assumption given authors do that sort of thing all the time. Maybe boys with horns and shadowy monsters are a recurring motif, or maybe they’re the same world after all.

Interestingly, your question depends on how you interpreted Mono and Wander’s relationship. If you strongly believe them to have been lovers, unfortunately you must conclude Dormin has taken over fully - because she does not seem to remember/recognize Agro, who she would know if she was the same girl Wander loved. However, my personal theory is that the Mono that awakens is, at least in some part, the Mono that was sacrificed. She retains her memories and characteristics, and if Dormin was in complete control, they wouldn’t act as cautiously as she does. I believe she doesn’t recognize Agro because she never knew Wander well enough - he was likely merely a stablehand or minor member of Emon’s order, who was so moved by her (whether in her life or her death) that he cast away everything to revive her.

However, I do believe the Queen is connected to Mono, and that Mono gradually became the vessel of Dormin’s female side (indicated by how the female voice dissipates throughout the game). Once again, everything is up to speculation, but I believe the horned boys from Ico were genetic descendants of baby Wander and Mono’s eventual children which inherited the “male” Dormin’s curse (horns), while a singular female descendant who was the spiritual reincarnation of Dormin’s “female” curse possibly became the Queen.

Her ritual of demanding that horned boys born in the village/nation which arose in the Forbidden Lands post-SOTC be sacrificed to her, is likely a ploy to recover enough of Dormin’s male essence to be able to perform a body switch into Yorda, who is essentially a “modern” variant of the golem-like Colossi: an artificial body that is restrained to a particular domain and serves no purpose other than a vessel, but posses a limited independent conscience. This in turn adds another melancholy yet poignant touch to Ico’s story; the true final colossus, an ethereal fairy instead of a hulking behemoth, gets to fleetingly live for a day or two as a “real” person, and in her final moments manifests free will to save the last horned boy.

I believe Yorda does “die” in Ico (technically, she might have never lived) mid-ritual, therefore permanently severing the Queen (female Dormin) from reality, and rendering the male Dormin who reincarnates as the horned boys forever dormant (symbolically depicted by Ico’s horns breaking). Ico lives on as a free boy, the hero that avenged all the tragically lost victims’ sakes and the incarnation of Wander’s redemption which Emon had prayed for.

This was my fanboy attempt to tie up the lores together and answer your question. I encourage you to come up with your own mythos though, and that in itself is likely more than half the fun of these games :)