Former EastEnders actress Sian Blake and her two young sons, Zachary and Amon, died as a result of head and neck injuries, police said.
Scotland Yard confirmed they were investigating a triple murder following the discovery of three bodies hidden in the garden of the family home on Tuesday.
Police sniffer dogs led officers to make the grim find at the property in Erith, Kent where "significant attempts" had been made to conceal the family's remains.
Ms Blake, 43, Zachary, eight, and Amon, four, have now been formally identified and post-mortem examinations have taken place.
Arthur Simpson-Kent, Ms Blake's former partner, is still being sought by police in connection with the murder inquiry and is believed to have fled the country to Ghana.
Photographs of Simpson-Kent, 48, were obtained by ITV News of Simpson-Kent at Kotoka Airport in the Ghanaian capital Accra - three days after he was quizzed by police over the family's disappearance.
It is understood concerns about domestic violence were raised by a relative of Ms Blake to the NSPCC on December 16, information which was passed on to the Metropolitan Police and Bexley Council.
A missing person's investigation was launched on the same day after police visited the home.
Murder detectives helped lead a forensic search of the property on Sunday after being drafted in to assist the borough force.
Earlier, Ms Blake's sister Ava said Simpson-Kent will have to "answer to God" for his alleged actions.
Speaking at Scotland Yard, she said: "Unfortunately I believe Arthur was responsible for my sister and my (nephews') deaths.
"I want him to face justice and explain why. It's my nephews more than anything.
"My brother is angry. My cousins are angry and it's because of the boys.
"They are angry about Sian, but the boys have devastated us. We have lost a generation. We can never replace them.
"I want him to be brought back to justice. He'll have to answer to the courts of this land and to God eventually."
Ms Blake, 43, had motor neurone disease - a fatal, rapidly progressing illness which affects the brain and spinal cord - and was reportedly looking "very frail" before she vanished.
She was last seen with her sons in Waltham Forest, east London, on December 13 and officers spoke to Simpson-Kent three days later at the family home in Pembroke Road, Erith.
Miss Blake, 51, said her sister had told their mother, Pansy, that she wanted to get out of her relationship "a long time ago".
She said: "In our opinion the relationship had already come to an end but she hadn't quite made that break or that decision to leave Arthur."
Miss Blake said she suspected texts claiming to be from her sister after she disappeared had not been written by her because she did not use "text lingo" and the messages were "poor grammatically" and contained "bad spelling".
The texts claimed Ms Blake was going away "for a few weeks", then it became "a few months", Miss Blake said.
Detective Superintendent Paul Monk said: "We are continuing to appeal for any information about the movements of Arthur Simpson-Kent who was last seen by police officers at his home in Erith on 16 December.
"If anyone has any information that they think might help our investigation then I would urge them to get in contact with us."
Ms Blake, who played soul singer Frankie in EastEnders, appeared in the BBC soap for 56 episodes between 1996 and 1997, reportedly quitting because of hostility from viewers towards her manipulative character.