I feel like so much of incest JAV has deceptive overtones. But it sounds like you're more into the "unknowingly having sex with a family member" rather than the "tricked into having sex with a family member" right? Because there are tons of vids where family members are tricked into having sex at first and just knowingly go along with it.
To answer your question, this is the whole premise of the 実録・近親相姦 (Memoir/Incest) series by Go-go-zu. A guy/girl wants to have sex with a family member, contacts a documentary producer to arrange it, the family member is blindfolded and has sex with a stranger before the guy/girl takes their place and fulfills their dream. They have a lot of movies in this series, but the earlier ones had a lot less actual incest in them and was more about voyeurism, so I find the early ones less interesting.
If you can access DMM then here's the full list.
https://www.dmm.co.jp/mono/dvd/-/list/=/article=series/id=206535/
The only other movie I can think of is SDMT-840 - Cinematic drama where two people participate in a game in which they have sex with each other separated by a curtain so they can't see each other. When the curtain is unveiled, it turns out they were father and daughter.
Honestly, mistaken identity because of a mask/costume seems like a fun idea, especially for Halloween. Shame I can't really think of any studio that does it.
Here are some other movies off the top of my head that might fulfill the spirit of what you're looking for, but I'm not sure.
POST-062 - A mom and son are picked up off the street and are hynoptized into having sex with each other. The hypnosis is snapped off right after they've had sex so you can see their reaction. I don't know if hynosis counts for you, but there are tons of hypnosis vids out there too.
IENE-370 - Sister has an accident and ends up with amnesia, brother pretends to be her boyfriend and has sex wit her. This one is pushing it, I guess, in terms of the unknowing part?
IENE-149, IENE-246 - Two women are picked up off the street and are challenged to do sexual acts witha guy, but that guy turns out to be one of the women's sons. The mother and son hide their identities and reluctantly go along with the smaller stuff, but the acts keep getting more and more heavy. This is probably not what you're looking for, but I'm recommending it anyway because the nonverbal acting can get pretty good and it does have an aspect of hidden identity. There are other movies in this series with F/D, B/S too, but I like the mom ones the best.
Oh and there's a movie that I can't remember in which a girl is kidnapped and her father is blindfolded and forced to have sex with her. It was more straight up r*** rather than being tricked so it's not really my thing. I'm not even sure if I'm remembering it correctly.
