A jury found Mick and Mairead Philpott guilty of the killing of the six siblings, aged 5 to 13, in a house fire in Derby, central England, in May 2012. Paul Mosley, a friend of the couple, was also convicted of manslaughter.
Prosecutors said the three hatched a plan to start the gasoline-fueled fire to blame Mick Philpott's former mistress and gain favor for him in family court proceedings.
The three were said to have planned to get all the children to sleep in one bedroom so that they could be rescued through a window when the fire started. But prosecutor Richard Latham said the plan went wrong within minutes, because the fire was far bigger than expected and the father was unable to smash a window to get in.
The children were asleep in their beds when the fire started. Five of them died that morning, and the sixth died three days later in the hospital.
The defendants will be sentenced Wednesday.