Estranged brothers Rahul (Fawad Afzal Khan) and Arjun (Sidharth Malhotra) find themselves drawn back to their childhood home in Coonoor when their elderly grandfather Amarjeet (Rishi Kapoor) suffers a heart attack. As they gather under one roof, their parents, Harsh (Rajat Kapoor) and Sunita Kapoor (Ratna Pathak), are also enveloped in their own marital strife.
Rahul, a successful writer based in London, carries the burden of expectations as the family's golden child, while Arjun, a struggling New Jersey bartender, grapples with feelings of inadequacy and jealousy. The stark contrast in their lives is only magnified when Arjun discovers that his childhood room has been transformed into a storage space, unlike Rahul’s room, preserved untouched. Tension brews as Arjun confronts Harsh about his disapproval of Arjun’s career choices, as Harsh insists that Arjun should listen to him.
Meanwhile, the brothers’ parents are dealing with their own complicated issues. Sunita dreams of starting her own catering business, but Harsh's refusal to support her leads to a heated conflict when Sunita uncovers the truth about Harsh's old affair. The family's shared concerns come to a head as they attempt to meet Amarjeet’s request to be buried with his comrades and to take a family photo—“Kapoor & Sons, since 1921”—on his 90th birthday, which is just around the corner.
As the brothers navigate family tensions, Arjun reestablishes a connection with his old friend Wasim (Sukant Goel) and meets Tia Malik (Alia Bhatt), who quickly captures his interest. Their budding romance, however, becomes complicated when Rahul also develops feelings for Tia after they share an adventurous night out, illuminating the complexities of love and loyalty among family ties.
Amarjeet’s health continues to deteriorate, leading to tough financial discussions about his medical treatment, sparking further strife between Harsh and Sunita over their financial decisions. Arjun's discovery that Rahul was reading his unfinished manuscript ignites a passionate confrontation, revealing deep-rooted issues between the brothers about their personal and professional lives.
As Amarjeet’s birthday celebration unfolds, the family reunion spirals into chaos with the unexpected arrival of Harsh’s mistress. Tensions rise, reframing relationships as painful secrets come to light, pushing family bonds to their limits.
Despite the fallout, the brothers ultimately find common ground as they fulfill their grandfather's final wish for a family photo. In doing so, they confront their past mistakes, mend their relationship, and begin to heal. In a touching conclusion, they learn to embrace their complexities as a family, culminating in “Kapoor & Sons, since 1921” becoming more than just a title, but a testament to love, understanding, and unity amidst life's challenges.
