Sharafat Gola told police that his brother - Ashraf Gola, a former chairman of a district council - was travelling along with a friend Iftikhar Ahmed in a car when unidentified men intercepted it near Pind Dadan Khan, some 250 kilometres from Lahore, and sprayed it with bullets leaving both dead.
Sharafat said his brother was recently acquitted in a blasphemy case but those pursuing it had threatened him of dire consequences.
The district and sessions judge had acquitted Ashraf as nothing was established against him.
The incident highlights how blasphemy accused are not safe in Pakistan even after being acquitted.
Earlier, another blasphemy accused had been shot dead after he secured bail in Punjab.
Human rights groups have alleged that Pakistan's blasphemy law is often misused to settle personal scores and grudges.