The injured man was treated by NSW Ambulance paramedics and taken to Liverpool Hospital in a critical condition.
He died about 9am, according to NSW Police.
A 47-year-old man, who is known to police, was arrested after attending Blacktown Police Station about 5.30am.
He has since been charged with two counts of murder.
The man was refused bail and is expected to face court on Monday.
Addressing media on Sunday, NSW Police Superintendent Jason Joyce said the incident appeared to be domestic violence-related.
“We believe that the deceased female and deceased male were in a relationship,” he said.
“The male that’s in custody was previously in a relationship with the female.”
Police have established crime scenes at the Quakers Hill residence, a service station on Richmond Rd in Woodcroft where a knife was recovered and the residence of the male currently in custody.
Superintendent Joyce said emergency services and neighbours were faced with “traumatic” and “confronting” scenes, with both victims sustaining multiple stab wounds.
A neighbour told , he heard about four “wordless screams of fear” followed by dogs barking and then “pure silence” until police arrived.
The officer stressed the investigation was in its infancy and called for anyone with information or CCTV to come forward.
“At this stage, we’re just aware that the male and female deceased were at that location when the incident occurred … the person who’s currently in custody arrived at some point during the night,” he said.
Shocked neighbours described hearing a commotion about 4.30am on Sunday.
“There was a couple of brief crashes … and then a lady screamed,” one resident told the ABC.
Police have urged any witnesses or anyone with CCTV or dashcam footage between 4.30am and 5.30am to contact Crime Stoppers on 1800 333 000.
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