Fobidden Comfort (FutaXM or F) (Siblings)

This is the story of a pair of siblings.  One futa, the other either her brother or sister.  I could play either side of it.  The idea is on side a futa constantly bullied and harassed just for being a futa.  On the other end, her sibling.  A quiet anti-social boy or girl that has a lot of trouble making friends or interacting with anyone outside the family.  Neither of them have many people they can rely on.  They spend more time with each other and one night something happens.  Neither expected or planned it, but somehow the two end up having sex.  Just to feel what it's like?  Because they don't see any other way to get it?  Either way, a line is crossed, a new relationship develops.

Just a simple starting point, that could go any number of ways.  A strong mix of story and sex, an evolving relationship.  Both know it is wrong, that they must hide it.  But at the same time, they cannot stop.  Both want more and cannot stop looking at the other in new ways.

Will focus on the two, but depending on who is playing what other relatives might gradually be brought in.  Other siblings, one or both parents, maybe others.