Dad's explanation for Unna & Pran getting engaged was that, it would improve Pran's image in the business world. He explained that Unna is very skilled and has excellent work ethics. She can manage huge corporations really well. Together Pran and Unna would be the power couple to bring GLS into the international market.
I don't think Dad's reasoning is all business though... that may be what he says, but I think he knows that Pran loves Unna and that Non at least cares a lot for Pat. He saw how Non treats Pat. And what he said to Non wasn't meant to keep him away from Pat, he was actually asking him if Non being that cruel to Pat (in Pran's disguise) was really necessary. Dad said, "you schemed to marry her to investigate on the embezzlement matter, and now you're being unusually mean to her. If Pat finds out the truth, how will you explain yourself?" He actually doesn't want Non to be mean to Pat. I think by now everyone knows Pat isn't the culprit.
Non being mean to Pat is his way of "punishing" her for her mean comments. He has an inferiority complex issue concerning his brother. And it seems Pran has the same thing towards Non. They just want the women they love to only look at them. Pat WAS harsh when she said she didn't love him and their intimate times were just a passing moment... I'd be hurt and pissed too. He can't control his frustrations around Pat. He wants to lash out at her but at the same time it looks like he wants to waist grab her all day, lolol