The incident was reported from east Delhi's Mandawli area.
Pratap Mohan, a retired Central Public Works Department (CPWD) employee, was thrashed by his elder son Rajkumar at his Mandawli resident where he lives with his other three sons, police said.
Rajkumar, who lives in Ghaziabad, went to Pratap Mohan's house and attacked him with a wooden stick. Pratap's hand was fractured in the assault.
"A case has been registered and an investigation is on. The accused is absconding," police said.