They were found wounded at a property in Elmshurst Crescent, East Finchley at about 06:25 BST.
The Metropolitan Police named the two victims  - said to have moved to the UK from Congo in central Africa - as Anny Ekofo, 52, and her nephew Bervil Ekofo, 21.
Mr Ekofo's mother said she had lost her "life" and her "best friend".
Maymie Botamba said: "He was my life, they have taken my life away. He was my best friend.
"He was so lovely and kind to everyone, always surrounded by girls. He had never been in trouble before, he had never been in a fight in his life."
The Met's homicide and major crime command unit is investigating.
Mrs Ekofo's cousin, Fifi Selo, said the family was in shock and "cannot explain what happened".
"They were an amazing family. Anny was the kind of person who was a mum to everybody. She always brought everybody together."
Both victims were pronounced dead at the scene, police said.
Local resident Lizzy Holsgrove said: "About 20 police cars and four or five paramedic cars, and three ambulances sped past my window.
"They cordoned off the street very quickly and police were sprinting from the top of the road where they'd stopped.
"There had been screaming before the police arrived."
Two people shot dead at a north London flat have been named locally as a mother of nine and her nephew.