I think it's down to the relationship between parent and child not going in that direction as well... I wish I could explain what it is that makes it so wrong.. I know your family are technically no different to any other human being Even if society or religion didn't say it's wrong, having been abused by family members it just makes you feel sick to the pit of your stomach and confused and disgusting. Don't just think about whether you'd be inclined to tap that, think about what it'd do psychologically to
her. You all know how fucked up I turned out.
I felt it necessary to share that to give you another point to think carefully on.
And this is a whole different kettle of fish
http://en.m.wikipedia.org/wiki/Genetic_sexual_attraction
I'm not sure where I stand on siblings but adopted siblings and step siblings along with cousins I think could be excusable.. I don't know..