The auto-rickshaw, in which the four-member family was travelling from Goalpara to Dudhnoi, was hit by a speeding truck on National Highway-37 at Agia, killing the couple on the spot, the police said.
The two children were injured critically and have been referred to Guwahati Medical College and Hospital, sources said.
The dead have been identified as Sahadev Rabha and Archana Rabha, sources said.