Good to hear that you liked the majority of it.
I am not sure what you mean by your last sentence. Only Maeda has this characteristic.
Maeda has a brother fetish, Akira is his older sister, Mirai is his younger sister and then there is Nobume which how the families are might be a cousin funny enough which is all tied to Ren before the crash. the ones tied to Inei are Luna, Mei, Diana and Artemis which is was meet after the crash which is why so many want to be his sister. granted when I was younger I use to like incest but considering how Patreon cracks down on junk like it leads me to believe the only ones who can have a relationship with the main character is Inei side
Incest isn't my thing, so I'll say this:
Maeda does not have a fetish, she just spoils her brother, but not romantically (The reason why will be explained in future updates).
Akira's position was already explained in Chapter 4 (More in deepth if you talk to her as [I].)
Mirai isn't a potential LI, so just cute scenes with her.
Nobume is not MC's cousin. (Which I think is obvious.)
And one more thing, there will be more LI's for both [R] and [I].