Dhafer and Hussein al-Mutliq were found guilty of killing fellow Saudis Azeb and Mahdi al-Moamer in a dispute between the two families, the interior ministry said.
They were both executed in Najran, in the south, a ministry statement carried by the official SPA news agency said.
The executions so far this year include 47 for "terrorism" carried out in a single day on January 2.
