You can breed parent to offspring but not to sibling to sibling, so your answer is yes....
When breeding is done that way, you are stregnthning both the best of the breed traits and the worst, and you won't know which will be dominant in the kids....
So you really need to know what you are breeding for, and what your end goal is.....
for example....
If it's for a milking doe...you would not want to breed a doe with a poor udder with a buck whose dam had a poor udder..
That is the simple version...someone should pop up with a more detailed explanation for you... @OneFineAcre