How close is too close?

[keefy]

I am no genetics expert but I would have thought inbreeding in one circumstance to produce 1 child would not have much affect.
My thinking is if inbreeding continues down the line over many generations that is where these "defects" show themselves.

what if u and ur brother where dating 2 sisters???? where is the line with that

That isnt incest unless the 2 sisters were their sisters.