Egypt saw a great expansion in the popularity of the local custom of brother-sister marriage during the first two centuries of the AD era, especially among metropolites, a privileged class in the Roman province. Why did this custom unfamiliar to the Romans flourish under Roman rule? How did the practice of sibling marriage function in Romano-Egyptian society? These are the questions this article addresses. Previous scholarship has attributed the reason for such popularity to the introduction of a rigid status system, under which provincial elites needed to prove their ancestry in order to a...