Bhai..different logic for different pair! Some are based on same/similar posting habits. Some are based on their animosity/love for each other...
For example, VaGal and VP are fond of posting pictures in every post.
Uppili and Gowser have answer for each and every problem in this world ;-)
JBF and Denice just post their sensless posts which often go unanswered..
Jauhari and Gatita are extreme poles of English language ( Of their love, not their expertise)
what about the third one? 

what type of marriage is this I am male, JBF is also male on the basis of his handle name.
do you specialise in gay marriages.