if you root your phone, which is not legal, you can do this with reaching Whatsapp Preferences (data/data/com.whatsapp/shared_prefs/com.whatsapp_preferences.xml) then open XML and change value of “int name=”participants_size_limit” value=”100″. Now you ready. Hope it works mate. But i do not suggest you to do this. may cause some bugs or problems.
I am having same issue. Having rooted the my phone and made changes to the whatsapp xlm file it does not allow one to increase group number over 101. Help needed!!!