>>14318804>>14318829I'd say this is the right idea but makes some assumptions: mainly that the parents carry recessive (or even one or both carrying a dominant) genes for a negative trait.
One generation of inbreeding is likely not going to result in birth defects but each generation of inbreeding will increase the "build-up" of recessive genes being expressed in a negative way.
SO: Generation 5 of your inbred family is much more likely to have genetic defects than say, Generation 1 of your inbred family.
