Breeding brother to sister or offspring to parent isn't a big deal in snakes so long as you don't do it generation after generation. Once or twice, sure, but not more than that or you'll start having issues. Plus you don't know how often it was done in any particular snake's genetics so some people are wary about breeding back. When recessive morphs (like pieds or albinos or clowns) started coming in inbreeding was just about the only way to make more of those snakes for a while. You bred the male to females then either bred the daughters back to dad or the siblings to each other. Or the other way if your original snake was a female.