- Maybe but part of that doesn't account for the female Care or Tiara/Belle.
The note found in Care's bedroom appears to be about her father. The lines of the note that pop out here are "A young person walks into your school building. They walk in with you. You're holding their hands. They come out crying into their hands, because nobody will love them, not ever again." Survivors of childhood sexual abuse often end up with feelings of self-loathing and stigmatization, which can lead to them feeling that they either can't be loved or don't deserve it. The note's reference to a school points towards Marvin being Care's father, since it's known that he has a daughter and has some connection to the school.
A girl speculated to be Care herself is found on the lower floor of the shack with a giant daisy in it. Paul plucks the petals from the flower in an imitation of the "loves me, loves me not" game. In addition to representing her trichotillomania, the petal plucking could be a "deflowering" metaphor, which would explain why her sprite distorts after they've all been plucked; the distortion could symbolize her being traumatized by the event. The "loves me, loves me not" game may also represent conflicting feelings towards her father and confusion as to whether or not he loves her.
The final piece of evidence lies with the pets Randice, Toneth, and Roneth. Randice, being a flower, can pretty easily be linked to Care. Toneth is first seen in a painting in Even Care, where he is standing next to Randice. He's seen in person much later, when he appears during the encounter with the shadow man. Since the shadow man is implied to be Marvin, it would make sense that Toneth has some kind of connection to him. Roneth is a hybrid of Toneth and Randice, and is speculated to be their child, which leads one to conclude that Care was impregnated by her own father.
- Might be slightly Jossed, as Roneth, according to his description in one episode, is Toneth's half brother, however, that might depend on how one interprets "half brother"
- Also if you think about it: It's possible that Mike might have been their child, since the text "Mike was a gift." could potentially play in the fact that this man KNEW that he had a child with his own daughter...
Tiara/Belle is adopted
My evidence is that one of the themes of Petscop is the abuse that some adoptive parents deal their children and the fact that her her features (eyebrows, eyes, nose) aren't included in the Child Library on the grounds that she isn't family, which would suggest that she was 1) adopted, 2) kidnapped, or, 3), both. Granted, we don't know precisely what that note meant by "family" but I presume that the note refers to biological family, not adopted.
One could say that, since he couldn't keep or get a hold of Care and the fact the Mike died, Marvin decided to seek out other children for his nefarious purposes, coming across Tiara/Belle. Once he has her, he tries to recondition her, the which he fails at because she resists it (as implied by Quitter's Room and the lines "I am Tiara, not Bell(e)" or "I am not Tiara, which suggests conflicting thoughts).
Paul repeatedly indicates he is not familiar with many commonly known things. He finds himself turning doorknobs the wrong way, and he fails to recognize the Christmas Tree on the calendar, for instance. In addition, Paul's first experience with the Quitter's Room has him on the reflected side, not the default side, and frequently throughout the series, the direction of how something rotates is often indicative of something. The windmill changes the direction of it's rotation once Paul accesses it and uses the Tool within, and many of the things associated with him rotate in a counter-clockwise manner. If you were facing a door and you turned the doorknob to open it, with a mirror to your left, then your reflection would open the reflected door by turning the knob in the opposite direction.
- This is supported by the fact that when Marvin opens the controls section of the options menu in Petscop 20, the default configuration has the right and left buttons make you go left and right, respectively.