A 36-year-old man was critically injured while his wife and son were killed when an unidentified vehicle rammed their two-wheeler late Monday night in Okhla.
The deceased have been identified as Madhu Saxena and her 15-year-old son Saransh.
Madhu's husband, Satyendra Saxena, is critically injured and has been admitted at the AIIMS trauma centre with a head injury.
The victims are residents of Harinagar in Okhla.
According to police, the victims had gone to Madhu's parents' house in Khyala in west delhi for the weekend.
"They called me at 9pm yesterday, saying they were heading home. Just two hours later, we received a call from the police that they have had an accident," said Rajiv Saxena, Satyendra's elder brother.