Rajesh, 53, his wife Komal (47) and their 23-year-old daughter Kavita were allegedly stabbed to death at their home.
The couple's son, who had claimed to be out on a morning walk at around 5 am, had said he discovered his parents and sister being allegedly stabbed to death.
Cracking the case in a few hours, police said the son had murdered the three avenging a "humiliation" by his father and his parents' intent to pass on their property to his sister.
Police said the boy, who has been arrested, was planning the murder for a while and decided to execute it on his parents' wedding anniversary.
After the murder, a neighbour had reached out upon hearing a noise from the house.