You should not have any problems with THAT particular aspect whatsoever. But in any case, there is TONS of "line-breeding"(i.e. inbreeding) that is constantly done throughout the hobby all the time, and actually HAS to be done to achieve certain goals. And you HAVE to do a certain amount of it to establish certain morphs, or progressively enhance certain selective traits you are looking for.
It is usually only when it is done with siblings over and over again constantly that it tends to bring undesireable "like" traits to negatively affect the animal....e.g. lack of vigor, deformities, and a plethora of other things that are genetic that you cannot even begin to see from just looking at the snake. Even different types of "lethal" genes can leave a snake deformed inside the egg never to develop and hatch at all because it was genetically aborted from certain genes failing miserably very early on as well.
Many would most likely automatically suspect it was something they had to have done wrong in the incubation process, and certainly this happens very often without a doubt too, but I am sure a smaller portion of these occurrences happen now and then from certain bloodlines of snakes being bred together constantly and things going wrong within the egg itself.
The "bug-eyed" trait in leucistic Texas Rat's is a prime example of a non-desireable "tandem" trait that goes hand-n-hand with certain bloodlines that gets expressed quite often and is likely due to them constantly being in-bred long ago to produce as many as possible into the market, instead of early on introducing new blood from good "normal" stock to help eliminate that problem early on.
In any case, these are just a couple examples of what "can" happen when it is CONSTANTLY done, but with that half-sib breeding you are thinking about doing should work just fine all things being equal.
Good luck! 
~Doug
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"a snake in the grass is a GOOD thing" 
my website -serpentinespecialties.webs.com