Three-year-old Anisuzzaman Apurba, who was injured in a fire in the capital's Mugda on May 24, died at Dhaka Medical College Hospital yesterday afternoon.
The gas explosion killed his father Anwaruzzaman Shipon, mother Faria Zaman Mou and seven-year-old neighbour Arman.
Apurba died at the Burn Unit after fighting with eighty percent burns to his body for over a week.
Police suspected that gas from a water tank entered Shipon's room where he lit a cigarette which caused the fire. However, Mou earlier had claimed that an exploded electric-fan led to the accident.