Ronald Godfrey was arrested late on Thursday at the home of Florence Jeffrey, 70, his mother-in-law, in the Jericho area of Oxford.
Her body had been in the house for at least two days before being found by police; the bodies of Margaret Godfrey, 52, and Susan Godfrey, 22, were recovered a short time later from an address in Marston, five miles away. They were also thought to have been killed at least two days earlier.
Mr Godfrey, the boss of a cleaning company from Oxford, will appear at a special sitting of Oxford magistrates.
Last night, Thames Valley police said all three died from multiple fractures of the skull, probably caused by a hammer. It is understood dental records are to be used in identification because their injuries are so bad.
Neighbours in the picturesque villages - which have been used as locations in episodes of television's Inspector Morse - said they were shocked by the deaths, describing the Godfreys as a devoted and loving family.
The body of Mrs Jeffrey was found shortly before 10pm on Thursday after friends told police they had been unable to contact her. When two officers knocked at her semi-detached home in Nelson Street, Mr Godfrey answered the door. Mrs Jeffrey's body was found in an upstairs room.
Mr Godfrey, a former soldier and fireman, was questioned by officers led by Det Supt John Stowe at St Aldates police station in Oxford.
According to neighbours in the quiet Marston cul-de-sac where the family lived, Mr Godfrey and his wife had recently sold their three-bedroom semi-detached home for pounds 70,000 and were planning to retire to a bungalow at Eynsham, also in Oxfordshire.
Stan and Kay Fuller, who have known the Godfreys for 18 years, said they were a devoted family. 'They did everything they could together,' Mrs Fuller said. 'It was lovely to see them with one another. They both adored Susan, she was their only child and they would do anything for her. She was the apple of Ron's eye.'
Margaret Fulford, a midwife who lives near by, said: 'They were a very quiet family and kept themselves to themselves. It's bizarre that something like this should happen. In all the years they've lived here I've never heard any noise or fights coming from the house. They all seemed perfectly happy. I last saw the daughter a few days ago and she seemed fine.'
Another neighbour, who asked not to be named, said: 'I got to know them quite well when they moved in.
'This is unbelievable. I thought they were the perfect couple. They were always together and seemed to be very close and devoted.'
In Jericho, where Mrs Jeffrey was killed, the response was similar. Her regular postman, Mohammed Akram Ali, said: 'I've known her for years and years and she was extremely friendly and polite. That lady was so nice she wouldn't hurt a fly. She always had kind words to say.'
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