You have to simply install a app called as OGWhatsapp, which will not be available on the Google Play Store.
OGWhatsapp provides you to run two Whatsapp accounts on a single device.
We can say OGWhatsapp is an updated version of Whatsapp,as the name from Osama Ghareeb(founder of OGWhatsapp).
Features of OGWhatsapp:
1) You can change the icon of Whatsappp Messenger
2) You can use two numbers on one device
3) You can save and also restore your backup.
1) Download OGWhatsapp from here.
2) Create a backup of your Whatsapp Messenger.
3) Uninstall Whatsapp Messenger ( Settings-> Apps-> Whatsapp-> Uninstall)
4)Rename your Whatsapp folder in your SD Card to OGWhatsapp.
5) In OGWhatsapp, verify your old number and whereas in official Whatsapp Messenger, verify with a new number.