A 51-year-old woman was killed by her 56-year-old former lover in a rage.
Detectives are treating her death as murder.
Her son, who is his 30s, was found with a number of stab wounds. His death is being treated as attempted murder.
Detectives from the PSNI’s Major Investigation Team are not looking for anyone else in connection with the stabbings.
Detectives remain at the scene in the Abbey Road area of Lisnaskea, Co Fermanagh.
Detective Chief Inspector Eamon Corrigan said: “Post mortem examinations will be carried out in due course and at this stage we are working to establish the circumstances surrounding the incident.
“Although our enquiries are at an early stage, we are threating the death of the woman as murder.
“The injuries to a man, aged in his 30’s, who was also in the house at the time of the incident and who suffered stab wounds to his abdomen, is being treated as attempted murder.
“He is currently in hospital in a stable condition.
“We are not looking for anyone else in relation to the incident at this time.
“But I would ask anyone with any information which could assist us with our enquiries to contact detectives at the Incident Room in Lisnaskea on 101 quoting reference number 774 15/05/17.”