The Thottapilly family, Sandeep, his wife Soumya, 38, and their two children, 12-year-old Siddhant and his 9-year-old sister Saachi, embarked on a trip to Portland, Oregon from their Valencia residence on March 30.
The bodies of Jennifer and Sarah Hart were found March 26 inside the family's SUV, which had crashed at the rocky shoreline below a cliff in Mendocino County.
Finally, late on Thursday, the highway patrol said there had been no sign of the missing people, but the recovered objects - the vehicle parts and personal items - were confirmed by family members as belonging to the Thottapillys.
Dorothy, of Mersey Road in Cheltenham, Gloucestershire, also shares her home with her two adult sons and their collective four children, over whom she has guardianship.
The body was found on Friday on an exposed terrain which appeared to have covered by the Eel River within the last few days as a result of a recent weather storm which brought heavy rain to the area.
Police had previously said they believed the Hart family died in a suicide plunge from a scenic overlook.
Carpenter said the family stopped in the small town of Naselle, Washington, about 80 miles (128 kilometers) northwest of their Woodland, Washington, home, during their drive to the California cliff.
The vehicle itself and the four members of the Thottapilly family have not been recovered from the Eel River, which remains too unsafe for divers to enter, but searchers along the banks located numerous items consistent with a Honda vehicle and interior, and items consistent with a family traveling on vacation, the Mendocino County Sheriff's Office said in a statement.
They made headway over about 12 miles of river bank during two days of searching.
Sheriff deputies and the California Highway Patrol have been working since last week to locate and recover the vehicle.
Police identified their vehicle as a maroon or burgundy 2016 Honda Pilot with license plates 7MMX138. They were reported missing when they failed to arrive at a relative's home in San Jose for a Friday stopover.
"These items were of a personal nature and will not be described further at this time, but it does confirm the fact the vehicle that was seen going into the river was that of the Thottapilly family", the California Highway Patrol said.
The family was last heard from in the town of Klamath, Del Norte County, on April 5.
Sandeep, originally from Kerala, grew up in Surat city in Gujarat and settled down in the USA over 15 years ago.