Not a Close Relative
[QUALITIES CONDUCIVE TO A HAPPY CONJUGAL LIFE] Not a close relative. The eighth quality is that she should not be a close relative, as that would lessen desire. The Prophet* said, “Don't marry close relatives for then the child is born scrawny”; 59 that is to say, weak; such is the weakening effect it [marrying close relatives] has on desire. For desire is excited by the deep emotions which result from sight and touch; emotions are strengthened by whatever is unfamiliar and new. On the other hand, what is familiar and seen continuously renders the faculties incapable of fully appreciating it [desire], being affected by it, or becoming aroused through it. These are the qualities desired in women.