The Talwars and the Durrani's might be involved in some illegal activity, which came to the knowledge of Aarushi and Hemraj by chance.
Why is the Police and CBI not looking into that ascpect????
With the arrest of these servants, it is clear they are being framed. If you notice generally when ever the servants commit the crime they immediately fled the place.
Which very clearly proves the servants are being made the Scapegoat for some body more powerful and also financially strong.