Hello DarkCookie, had another idea for you to hopefully consider - this one dealing with the trap segment.
The first thing is to introduce a male twin to an existing female character - perhaps Mia (probably won't work due to her hairstyle, but let's work with this for now). Let's call this twin Mio (or Max, Milo, etc.) for the moment. Mio is very similar physically to his sister, except of course for the naughty bits - he comes off as a bit of angry loner, especially when in the PC's company. After the PC successfully seduces Mia (let's say to at least second base), the PC goes to Gym class and sees who he thinks is Mia bent over a drinking fountain. The PC, approaches and gropes the figure rather thoroughly, only to find himself pushed back from an angry Mio. The PC stutters out an excuse about mistaken identity, and Mio tells the PC off. Fortunately, no one appeared to have seen the altercation due to class being in session. The PC is very embarassed by the whole situation, but recalls feeling a hard object just about where Mio's anus is. Curious, the PC waits till the next day when Mio goes to the bathroom. The PC enters the bathroom and hears a slight moan. Creeping quietly to an open stall adjoining the one Mio is in, the PC stands on the toilet and oversees what's happening in the next stall. Within, Mio is masturbating while fucking himself with a dildo and even murmurs the PC's name. The PC is able to take a video of this before silently getting off the toilet. This is where the PC is given a decision about confronting Mio. Option 1, the PC blackmails Mio into helping Mia's seduction and ends Mio's portion of the quest-line (i.e. the no-homo option). Option 2, the PC blackmails Mio into confessing his desires and uses that to to seduce Mio - which gets help with Mia's seduction, as well as turning Mio into a quasi-girlfriend.
Some half-formed ideas involve the PC getting a BJ from Mio when another male character comes in who also confuses Mio for his sister. He asks permission to fuck Mio, but is told to do anal only. After fucking Mio, the male character leaves. This could lead to a chain of events where Mio's identity is revealed and turns Mio into the boy's cumdump... but honestly, this would be more like a bad end to Mio.
Another idea is to eventually have Mia discover Mio's hidden side, which leads to a possible threesome with the PC (depending on her affection level - it could also lead to the PC losing both). If successful, both Mia and Mio are fucked by the PC, with Mia and Mio taking turns or being sandwiched between the PC and their sibling (Mia can use a strap-on) - a repeatable encounter.