@Freyrs_storiesOkay, I've solved this. It was a solution to another problem that I was headed towards as part of a climax. thing is I'm not sure how long it is since this sort of thing is done any more.
The problem:
a brother and sister have an incestual relationship in the past. they are both teens at the time.
The brother is banished from the family never to return. he no longer exists as far as the parents are concerned.
about a year later the sister writes a letter to her brother, as a way of ending their relationship on her own terms. the mother finds the letter and despite there was no way to actually send it to the brother, also banishes the sister. but as she is still young she gets adopted by a friends family. so she gets a new name and everything.
the catch is that she also gets a new birth certificate that gives her a new mother and father. this means that when she marries her husband many years later she has to choose which birth certificate to use to marry under.
the reason for the court order is that the soon to be ex-husband finds out about the past (the teenage past) he does not (at the moment) find out about about the adult reunion relationship, though this was ended years before the husband comes into the picture.
So the solution is that the 'sister' has a different identity when she is married that separates her from the brother. it also means that there is room for the brother and sister to reunite again once the court order is overturned. I think I have to be careful with the dual identity thing lest it be deus-ex-machina.
to complicate matters I have to find a thread to stitch together so that the sister's twins who are also in an incestual relationship get together some how. The relationship builds over the course of the story, from just close twins showing compassion for each other turns sexual and romantic. not just pure teen lust.
Even though I'm 80K words in to the story I've barely described the twins, besides the son has his uncles 'eyes' and the daughter is petite. I'm fighting to work out how to have their hair the colours I want. I was thinking black for the boy and red for the girl but those are at opposite ends of the genetic pool as far as how colours are generated by melanin type proteins. the name of which escape me right now.
so there is a hint that the son looks like his uncle, so maybe something happened there? though we know nothing did. it's just ammo for the husband.
So I think I have an 'out', but its not the out I originally envisaged but it may have to do.