This isn't "Dubious" it's flat out NONCONSENSUAL, it's RAPE VIA MIND CONTROL AND COERCION.
MC is losing his grip on reality (due to this brother entity) and believes he is potentially experiencing incestuous intrusive thoughts, when in reality he is being violated in both body and mind.
He has no control over what is happening or any idea that it is happening, not to mention he actively resists it when he can.
It's not "Dubious" just because the depiction is eroticized for the audience to get off on.
The bare minimum is properly acknowledging the subject matter and tagging accordingly.
If you wanna get off on abuse, at the very least, you should not shy away or deny that fact and prove you can actually identify it.
I know this is senseless, unserious smut where a sadistic, obsessive bastard kidnaps and sexually tortures his crush...
But I am astounded by the top's resistance to using actual lube on a man he wants to penetrate ASAP and make feel good, knowing damn well the bottom does NOT have a self-lubricating asshole and constantly voices his discomfort.
Not to mention the dry urethral insertion.
(╬￣皿￣)凸