Mansour and Muhammad Azam were killed on May 21 when US special forces targeted their vehicle with a drone in Noshki district of Balochistan province while allegedly returning from Iran by road.
A senior police official said that Azam's brother Muhammad Qasim had filed a First Information Report (FIR) against the US government at the Mal Levies station in Noshki district.
"His brother has in the report claimed that Azam was not a terrorist and the father of four children and the sole bread earner of the family," the official said.
"We want justice," Azam's uncle, Haji Khuda-i-Nazar, told Dawn News on Sunday.
"We want to bring the perpetrators of the drone strike to justice. My nephew Muhammad Azam was innocent and had no links to any terror group."
Pakistan government has described the drone strike as a violation of its sovereignty.