Lu Dongming, 45, and his 24-year-old nephew Lu Kuan were sentenced to death by a court in Anhui province in eastern China for the two bombings in May this year, Xinhua news agency reported.
Lu's 19-year-old son was also convicted as an accessory to the crimes and sentenced to 10 years in prison, it said.
The gang was also convicted of threatening to bomb other Internet cafes if they failed to pay them money, it added.
Four other people were injured in the home-made time-bomb attacks, which were both detonated on the evening of May 5, the report said.

Copyright AFP (Agence France-Presse), 2006