The shaming over the discovery of pornography,,could of had an effect, on you.
What, happened, to your brother?
The five year old behavior of yourself, doesn't necessarily mean, you'd been sexually molested prior, your aggressive behavior, about it, could mean home life was volatile, but doesn't mean nothing prior, either. Being in touch with early memories, is difficult.
Off the top of my head, i can't think of why rape fantasies are common. They just are, it's fantasy.
Something, to work through, in therapy.

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