A spokesman for the Norfolk district attorney's office confirmed the deaths Monday.
Police responded to the Franklin home at about 8 p.m. Sunday after other family members found the children together inside the chest that could only be opened from the outside. The children were taken to hospitals but did not survive.
The chest was close to a television that had the volume turned up high.
Authorities say the deaths appear to be accidental, but autopsies are scheduled. Relatives are cooperating.
No names were released.
The Franklin schools say both children attended an elementary school in town and counselors are available to students and staff.