Yashvardhan "Yash" Raichand (Amitabh Bachchan) is a billionaire business tycoon living in Delhi with his wife Nandini (Jaya Bachchan) and two sons Rahul and Rohan. The Raichand household is highly patriarchal and strictly follows traditions. Rahul is the elder son and was adopted by Yash and Nandini at birth. This is known to everyone in the household except Rohan.
Adult Rahul (Shahrukh Khan) returns home after completing his education abroad and falls in love with the vivacious Anjali Sharma (Kajol). However, their love is forbidden because Anjali is from a low-income background. During this time, Rohan, still a child, is sent to boarding school. Yash announces his desire for Rahul to marry Naina (Rani Mukherji), a high-society woman and Rahul's childhood friend, as Yash believes that parents have the right to choose their child's spouse. However, when he comes to know of Anjali, he is enraged due to her status, and Rahul promises not to marry her, as he does not want to hurt his father. However, Rahul discovers that Anjali's father (Alok Nath) has died, leaving behind Anjali and her kid sister Pooja. He spontaneously decides to marry her despite his father's hostility. When he brings Anjali home, Yash disowns Rahul, reminding him of his adopted status. Hurt by this, Rahul shares a tearful goodbye with Nandini and leaves home. Rohan never finds out the truth of why Rahul left home.
Ten years later, an adult Rohan (Hrithik Roshan) returns home from boarding school and finally learns from his grandmothers why Rahul left as well as the fact that he is actually adopted. Seeing the pain that this separation has brought upon his parents, Rohan vows to reunite the family. He learns that Rahul, Anjali, and Pooja have moved to London, and travels there, lying to his parents that it is to pursue further studies. In London, Rahul and Anjali live happily with a young son, Krish, and Pooja (Kareena Kapoor), now a beautiful and ultra-modern diva studying at King's College London. Rohan and Pooja, who were childhood friends in the past after their elder siblings fell in love, reunite and she supports him in his quest to bring his brother and sister-in-law back home. Rohan poses as Pooja's friend who has come from India and Rahul agrees to let him live with them after Rohan introduces himself as "Yash" to hide his real identity: Rahul does not recognize his immensely-changed now-adult brother after so many years. At Krish's school function, when Pooja asks Krish how he got over his stage nerves, he recites some advice that Rohan had given him. Rahul, having given Rohan this exact advice ten years ago, hears Krish and finally realizes that "Yash" is actually his brother. ReadMore>