No, not really. Breeding siblings isn't ideal but inbreeding is a quite misunderstood topic in rabbits. If you keep doing it for generations without culling out every negative trait that pops up and let it accumulate that's how you create bad genetics. If you do it right, that's how all our breeds were created, although there is more to that. Same without inbreeding, do not breed any rabbits that have issues (health, behaviour....). Just multiplying rabbits without scrutiny or with the wrong goals is an issue, think about all those cute rabbit teeth issues and lop ear problems. Breeders selected domestic rabbits that way for a long time, so many of possible bad gene variations are rare or gone - so a single accidential inbreeding hasn't really more risks than unrelated rabbits.
