Damn that could be interesting xd.
Yeah... unfortunately there no such games. Maybe in the game "Corruption" but there is no other game where e.g. a son shares his mom with his best friend or something close to mom-swapping between friends/cousins.
some games I found:This is precisely why I get frustrated when someone says this type of content is "repetitive" or "the author doesn't have enough creativity", there are hundreds of scenarios a developer could write on this genre and for the most part, demand isn't really satisfied since it's a more niche crowd, hundreds of scenarios that were never written before making it easier to not write a cliche. This is prime time for devs.
Mom's report you are on an adventure with your mom and you can command her to have sex with other men to get information
MamaShota RPG incest and all type of NTR
Take Over you can prostitute/share your mom and sister
in all of this there is the incest option