Anonymous3: A lot more than that even Anon2. The reason it's discouraged is more because it severely weakens the genepool passed through those kids. Just look at the state of European royalty in the late 19th century (rampant blood diseases, weakened immune systems, etc) or the later rulers of the Ptolemaic Dynasty (lots of mental ailments, paranoia, schizophrenia).
One or two generations of inbreeding isn't going to cause 'tard babies, but minor problems will exponentially grow with every generation until they're debilitating.
One or two generations of inbreeding isn't going to cause 'tard babies, but minor problems will exponentially grow with every generation until they're debilitating.