can you breed siblings?

[Mendel's Balls]

sibling x sibling =no
offspring x parent = okay for about 1-2 generations but after that you will get deformities(ex:eye problems)

edit:i forgot to mention its possible to breed siblings but not recomended.

Please give a rationale for why sib to sib crosses are not okay or recommended. Parents and offspring share 50% of their total genetic material while full siblings also share 50% of their genetic material.