Martha Parker (daughter of Gene Costner) and Hershel Parker
Doris Miles (daughter of Gene's sister, Ida Costner Edwards) and Hayes Miles
But this is Mississippi, so the sons are not merely Costner 2nd cousins. They are also Bell cousins through Doris's husband Victor and they are also Dougherty cousins through Doris's husband Victor. Time to devise a consanguinity chart.