For some reason both the families have exchanged their kids. Anurag was born to Tani's mom but she gave him to Anu's Mom may be because they wanted a male child (That explains why Anu is fat- he has taken after his Mom!). Then when Tani was born to Anurag's mom she was given to the other lady. So they decided later that instead of exchanging their kids back... lets get them married đđđđđ
Anurag's so-called family is actually not his family.. So now they hv left him in the mental asylum and they don't care. They only care about Tani who is their real daughter. Tani's so-called parents must have died or something. So Anurag is left with no family.