Two couples with the same surnames pursue In-Vitro fertilization and wait for their upcoming babies. Trouble ensues when they find that each couple's sperm has been swapped. Varun Batra (Akshay Kumar) is a salesman at a Volkswagen dealership and a good one at that. Deepti Batra (Kareena Kapoor Khan) is his spunky wife. They are trying hard for a kid, but its not working out. Varun feels pressured for sex and is unable to perform in bed.His sister Richa (Anjana Sukhani) suggests that they visit an IVF specialist Dr Anand Joshi (Adil Hussain), who explains that the duo will have to undergo In-Vitro fertilization to conceive a child. Varun has a crush on Anand's wife Dr. Sandhya Joshi (Tisca Chopra)After the IVF is complete, 12 days later Sandhya calls Deepti in for an emergency check-up. At the clinic the due meet Honey Batra (Diljit Dosanjh) and Monika Batra (Kiara Advani). Anand and Sandhya explain that due to the same surname, the sperm got mixed up. Which means Honey's sperm in Deepti's egg, inside Deepti and Varun's sperm in Monika's egg inside Monika.Despite long odds, both ladies get pregnant. Varun wants Deepti to abort. Varun considers Honey to be an imbecile and simply cannot bear the thought of his genes in a child that Deepti would bring up. Varun wants to abort vehemently, but Deepti is not sure. Varun even tells Honey that he doesn't consider the kid inside Deepti as his own. Honey and Monika are different, they consider both kids as their own (the one inside Monika and the one inside Deepti) To ensure that Deepti and Varun don't abort, they buy an apartment next to Varun and move in.Honey even suggests that after delivery Deepti hands over her kid to Monika. Deepti is livid at the suggestion, but Varun is cool. Deepti asks Richa to draw up a legal contract that states that after delivery both families won't have any rights over each other's kids. But when they call Monika and Honey for the signing, they bring their own contract stating how their kid inside Deepti should be brought up and his / her career choices. It's clear that Honey and Monika want deeper relations while Deepti and Varun want to exit any possible relations.Deepti reaches out to Monika, and both connect. Monika tells Deepti has she had a miscarriage twice before. Varun and Honey end up fighting when Honey demands that Deepti quits her job to take care of his child. This happens in a bar where Honey misbehaves and is thus locked up after Varun leaves. That night Monika has pains and asks Varun to help out. He takes her to the hospital. Monika gives birth to a girl, prematurely, but her chances of survival are slim. Varun cries as Honey comes to the hospital.Varun completely changes 180 degrees and hugs Deepti and his kid inside her. Monika's kid survives and Monika and Honey take her home with great pomp and celebration. Deepti and Varun participate 100% in her recovery. 2 months later, Deepti goes into labor and at the precise moment, Varun gets a slip disc. Honey takes Deepti and Varun to the hospital. Deepti has a baby girl as well.