rn Yashvardhan "Yash" Raichand (Amitabh Bachchan) is a rich businessman, living in New Delhi with his wife Nandini (Jaya Bachchan) and his two sons, Rahul and Rohan. The elder son, Rahul is adopted whilst Rohan is their biological son. As a result, Rahul feels indebted to his parents when he finds out (at the age of eight) about his adoption. As an adult, Rahul (Shahrukh Khan) falls in love with Anjali Sharma (Kajol), a girl belonging to a lower social standing than him, against the wishes of Yash, who wants him to marry Naina Kapoor (Rani Mukerji). Rahul, however, rebels and marries Anjali, following which Yash disowns Rahul as his son. Disheartened, Rahul leaves for London with his wife. Nandini sends Sayeeda (Farida Jalal), Rahul and Rohan's nanny, after Rahul to take care of him. Meanwhile, Rohan is sent to a boarding school, as per family tradition.
rn Ten years later, a grown-up Rohan (Hrithik Roshan) finds out the truth about Rahul's disappearance. He asks his parents to let him go to London to attend graduate school; but he does so in order to conspire with Anjali's sister, Pooja "Poo" Sharma (Kareena Kapoor) to bring his brother back home. Poo informs Rahul that Rohan is her friend's cousin who has shifted from India to London to pursue his studies and needs a place to stay. Rahul reluctantly agrees to let him live with them. When Rahul eventually finds out about Rohan's identity, Rohan begs of him to return home. Rahul refuses, as he believes that Yash does not love him. Poo, however, believes that Rahul will go back home, so she encourages Rohan to invite his parents over to London and arrange for them to meet Rahul. Once in London, Nandini and Rahul share a happy reunion. But Rahul refuses to talk to his father. Meanwhile, Yash finds out about the conspiracy and is furious with Rohan. He and Nandini, however, return to India due to the sudden death of his mother (Achala Sachdev).
rn Rahul, who also joins Yash and Rohan during the funeral service, agrees to return home for one visit to meet his mother, on the insistence of Rohan and Poo. Once there, Yash expresses his guilt for disowning his elder son, and adds that Rahul was foolish enough for believing that his father did not love him. The film ends with an elaborate wedding ceremony of Rohan and Poo, in which the entire family participates.