The victims were named locally as Margaret Harris, 78, and her daughter Sharon, 55.
Mrs Harris’s husband David, 76, was seriously injured and taken by air ambulance to a London hospital.
A 28-year-old man was arrested on suspicion of murder last night and is in police custody.
Neighbours said there had been complaints about noise at the family house in Hadlow, near Tonbridge, Kent, and a motor home parked there.
One said: “You don’t expect anything like this to happen. I have never heard of anything like this before in the village.”
Keith Ford, 71, said: “There were problems with their motor home, which they would park in the road and the drive. They had six cars between them.”
Sophie Moorey-Brown, 31, said: “We’ve lived here for five years and never heard anything bad happen. It has always been so quiet and a lovely place to be.”
Mr and Mrs Harris lived with another son, Christopher, 51, in the ex-council home the couple had owned since 1988.
Neighbours said both Sharon and Christopher had worked locally for housewares manufacturer Salter.
Kent police refused to confirm if officers had previously visited the address or if it was a neighbour dispute, but said the victims were believed to have known their attacker.
The force said officers were called to the scene in Carpenters Lane at 7.41am by ambulance crews trying to save the two women.
The victims were later pronounced dead at the scene. A police spokesman said: “Officers arrested a 28-year-old man on suspicion of murder.
“He remains in police custody.”
A woman in her 30s was held on suspicion of murder yesterday after a man, also in his 30s, was fatally stabbed in the village of Bugle, Cornwall, on Friday.