There is a genetic link in the causation of osteoarthritis. Twin studies have been used to prove this. You didn't say if you and your brother are identical or fraternal twins. This seems to make a difference.

Identical twins are twice as likely to show an increased rate of hip arthritis as fraternal twins. The rate is much higher in female twins.

Even if you weren't twins, your risk of developing OA is higher just being siblings. A 1997 study of sibling risk showed that brothers and sisters of patients who had a total hip replacement were twice as likely to have a hip replacement themselves. Not only that, but their risk of a knee replacement was five times higher.