The story is about the love and affection shared between brothers and unity within a family. Ramkishen (Alok Nath) and his wife Mamta (Reema Lagoo) live with their three sons, Vivek (Mohnish Behl), Prem (Salman Khan), and Vinod (Saif Ali Khan). Prem and Vinod have sweethearts in Preeti and Sapna (Sonali Bendre and Karisma Kapoor), but the eldest son Vivek has always been shy due to a birth handicap. The family meets with Adarsh and his daughter Sangeeta (Rajeev Verma and Tabu), and decide to get Sangeeta and Vivek get married. After their wedding Mamta becomes insecure, assuming that Vivek (her step-son) would become selfish and take over the business. To protect Prem and Vinod, Mamta schemes with Dhanraj (Sadashiv Amrapurkar) to alienate Vivek from the inheritance. This divides the family. Due to the love for his elder brother, Prem quietly revolts against his mother's decision and changes her heart. Hum Saath Saath Hain restores faith in the Indian concept of a joint family.