The fire started around 1:30 a.m. at the house on Tran Cao Van Street in Thanh Khe District.
The couple who owned the house and their youngest son, who is 9 years old, were able to escape the fire through the front door.
The three of them were sleeping on the first floor when fire engulfed the house.
However the two boys sleeping on the third floor could not get out. One of them is the oldest son of the couple and the other is their nephew.
The fire was put out at around 3 a.m.
By the time rescuers approached them on the third floor, the boys have already died of suffocation.
The house stretches 6m wide and has balconies on all floors.
Police are looking into the cause of the fire.