A quick search and I found that they recommend only breeding dogs with a hip score of less than 10. The average score for GSD is 13. So the brother with the 10 would not be the first choice to breed but not unacceptable as he is technically better than average.
When thinking about breeding you need to consider a lot more than hip scores. So if this boy has average hips, but fantastic temperament, drive, biddability, and his other relatives(littermates, mom,dad,aunts uncles, gparents, ) all have good hips, then you can consider using him.
I would also check his elbows.
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