These are some things I think should be answered within the story:
What was the relationship history
How did the attraction first occur
How reluctant were the people involved
Was the trigger a single event or multiple subtle changes
How did they find out about the attraction
Did they fight it
Who initiated first contact
What is the power dynamic
What pushed them to cross the boundary
Who controls the frequency of the encounters
How far would they go to keep it a secret
Who else knows
So, I actually am in the process of writing my own, and I asked myself similar questions when coming up with it. Mine is a twincest brother sister romance. As for your list
History: They grew up together, close as all twins tend to be.
Trigger: This is kinda nuanced but has to come before how the attraction occurs. My Trigger is a shared trauma
involving the death of their father.
How: Due to the circumstances surrounding that they became much closer, slept in the same bed, etc.
Reluctance: This will kinda depend on the player and options. Both twins are MC. You'll make decisions as both and they will affect relationship progression. The sister is reluctant for reasons related to their fathers death, the brother is less reluctant for the exact same reasons.
Finding out: The same way it would happen if they weren't siblings... one day the just can't hold it and bam.
Did they fight it: This relates to reluctance, no? I think the characters should have some personal battles with incest, but no more than that.
Who Initiates: In my game it'll most likely be the sister, but that has to do with details I'd rather not share. However because of the choice system it could be the brother if the sister doesn't.
Power Dynamic: This is one thing I would like to both address and avoid. The sister is worried about the power dynamic, its the source of her reluctance, but it's not like in DmD where the father is manipulating and corrupting the daughter.
What pushes them across the boundary: well which boundary? Their initial attraction their first kiss, their confessions, these will be the culmination of the events set in motion by the shared trauma. Sex? Well that will take more, but they're already teetering on that edge by the first kiss. The intimacy of sleeping together has kinda removed any barriers beyond social, and the trauma has removed the psychological.
Who controls the frequency: This isn't really relevant as my characters are in a romantic incestuous relationship. If there was a power dynamic or some sort of sexual gratification relationship then maybe but not here.
Secrecy: I'm actually still wrestling with this. I think a Dreaming of Dana type ending might be possible, but not the goal. I think that they'll simply hide their relationship behind the trauma. It gives them an excuse for how close they are that keeps even their mother from suspecting, at least for now.
Who else knows: I'm still debating on whether or not the mentor character behind the sister will know or not. Regardless there will be someone who urges her to accept her feelings. I just don't know if they'll be told the truth, it may be an option I give the player. Obviously if they go the Dreaming of Dana route then the beard will know, but it won't be necessary. The beard characters may also find out from other options along the way, but that isn't something I've committed to yet.
makes it all warm and fuzzy.
