• We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
Ask in the general modding forum, we really have enough work as it is without supporting modding questions.
The ck2 wiki has plenty of info too, good source.
 
In common/scripted_triggers/plus_scrupted_triggers.txt find may_create_duchy_trigger

In it between war and OR statement add "num_of_count_titles = 2" without quotes.