[Loren]

I agree with Rhea. Slight, occasional inbreeding most definitely happens in the wild. I would try to avoid repeated, close inbreeding like some breeders do though. They breed son to daughter, then grandson to grandmother, and so on, so they can bring out a trait. Many/most of the high dollar color morphs are extremely inbred. Then, after a few inbred generations, they outbreed them one generation, to get hets to breed together, and call them outbred.
But, as the breeders will tell you, there is nothing wrong with them, they eat and breed fine. The thing we dont see is what will be the long term effect on those bloodlines after several more generations.

As Rhea said, though, 2 pairs of snakes will give you unlimited amounts of males amd females to pair up together. Then, if you get so far as to raise up your favorite offspring from the 3rd generation, you can always find a new unrelated mate for them then- but thats years away, so I wouldnt worry about that snake yet.