Jennifer and Stephen Chapple, aged in their 30s, were killed in their home in a Somerset village.
A woman was stabbed to death in her home as her two children were asleep upstairs, police have said.
Jennifer and Stephen Chapple, who also died, were found at the house in Dragon Rise in Norton Fitzwarren, near Taunton, Somerset, on Sunday night.
Their children, aged five and six, were unhurt and are being looked after by family members.
Two men, aged 34 and 67, were arrested on suspicion of murder. The older man has been released under investigation.
Magistrates granted an extension to the custody time limit in relation to the younger man.
A post-mortem examination confirmed Mrs Chapple died from multiple stab wounds.
Investigations into Mr Chapple’s cause of death are ongoing.
Det Insp Neil Meade, of Avon and Somerset Police, said: “What happened to Stephen and Jennifer is utterly heart-breaking and I can’t begin to imagine the impact their deaths will have on their two children.
“This is a tragic incident which has shocked the community.”
Officers were called to the property at about 21:45 GMT. Cordons remain at two properties on the housing estate as officers continue to examine them.
Tributes have poured in to the couple since news of their deaths emerged.
Mr Chapple, 36, worked at West Somerset College. Headteacher Gregg Mockridge said he will be “sadly missed”.
“Steve was a fantastic colleague at West Somerset College, a brilliant teacher that cared deeply about the students in his care,” he said.
Mrs Chapple, 33, worked in the coffee shop at a garden centre in the village, where staff said they were “devastated” at the loss of their “much-loved friend”.