Badhai Ho in Hindi means Congratulations.
You can read the story line in this Wikipedia link
I could recognise only Neena Gupta, an actress form my early movie going days and Ayushmaan Khurana who acted in my last review Andha Dhun. These two literally carry the entire movie on their histrionics but, in all fairness, all the others extend excellent support.
The story line, dialogues and direction are simply brilliant. The portrayal of an ordinary middle class family caught in an embarrassing situation is portrayed with elan and all the nuances of their daily lives very lucidly brought out.
The story is unusual but, highly probable and for that precise reason so moving. I think that it deserves to be called a tragicomedy!
From all accounts, it is a box office hit without the help of songs, dance and/or fight scenes. A clean family movie which I recommend highly.