Christian do not support incest
the word "christian" has a lot of different meaning, from the guy that believe everyword of the bible is to be taken litterally, to the guy that was baptised and therefore is technically a christian but don't believe in god.
But if we are gonna be honest, incest is all over the Bible, i'm not sure if it is meant to be
poetic but it is what it is.
I can give you the verses where incest is present in the Bible if you are interested.
By the way, creationnist Ken Ham, in his debate against Bill Nye litterally said that incest was perfectly fine back in the early days of the earth (6000 years ago), as it is written in the Bible. Nothing wrong about incest back then, but now that we don't need to fuck our siblings anymore to reproduce, it is best to avoid incest (i don't remember exactly how he put it but it was along those lines)