Cheer up, we are only halfway into the game and they only commited recently, there is plenty of opportunity in the future for that stuff.Bummer. I didn't expect that gratuitous "fuck you" from Eva Kiss. Ian being into watching Jeremy fuck other girls and following Lena's salkfap was a missleading option from the get-go.
Either way, Jeremy fucking some girls that they probably already both fucked and they arent serious about them is quite different then Jeremy fucking his "gf", remember that even Jeremy declines Lena advances if Ian says that he is serious about her(you can persuade, but that the power of protagonist and he is pretty guilty afterwards), Jeremy is a nice bro, he is a bit simple but not stupid, when he ask you about Lena and if you say "its just for fun and not serious" he is pretty happy to fuck her, i bet there will be some threesome with Lena on "open" relationship route.
Probably after Emma threesome since it was already foreshadowed, i bet there would be some Louise action in the future if they are still together and you share girls, cant wait for that one for sure.