It's not love for Shehroz, it's her ego and weird competitive complex over Ushna. Remember how she would get mad every semester when Ushna got top grades and she would get asked about it? Sadaf always needs to one-up Ushna, like how she would point out her family's financial status and how hard it was for them to send her to university. And now? Now Ushna is married to a handsome millionaire husband that accepts everything about her background, adoption and all. Ushna is living the life that Sadaf dreamed for herself. How can she ever accept that from the Ushna that she always thought to be beneath her?
That's what Rafakat was talking about. I won't say that he is totally blame less as a working father, he himself has witnessed his kids getting spoilt by his wife, but chose to not say anything until now when he himself has started getting into trouble due to all their misdeeds, but Raeesa has huge role to play in their good for nothing upbringing. They have learnt from her to be dominating, weirdly competitive, disrespectful, jelous, not take 'no' as answer and many more. When Sufiyan demanded Ushna after Zainab's marriage and Sadaf was already Mrs. Shehroz inside her empty head, Raeesa could have just told them that maximum they can go at their home with a proposal. But she was giving them hope that she'll get them whatever they want with planning, plotting and manipulation. She'll take the advantage of Ushna's adoption secret and get things done keeping a gun on Zainab's head. When things really didn't go as per her planning, she doesn't have any secret to blackmail, both husband and wife want to tack a back seat, they have realised their kids won't stop even at the cost of destruction. They are ready to go ahead with their plotting at the cost of entire family getting destroyed. Because they were brought up with concept that concent doesn't matter. They were brought up with values like they are superior than Ushna. When Zainab said no for Ushna's marriage with an oldie selected by Raeesa and asked them to get Sadaf married with him if that's really good proposal, both R square said 'how could you compare our priceless princess with adopted ganda khoon'. So this is coming from parents' teaching that all humans are not equal, you should judge and treat them as per their financial background. And both brother and sister have learned it perfectly and that's the reason they are behind Ushna as they think she's not superior than them, Shehroz is. They were mistreated and insulted by Shehroz in worst possible way, but they would never plot to demean his character because they think him as superior. Maximum they say Shehroz ne achha Nahi Kiya'. But with Ushna who has never insulted them the way Shehroz has done, still they would plot to assassinate her character because they see her as inferior than them. They are just products of bad upbringing.
Today when R square are desperate to make them learn meaning of concent and telling them that those 2 people are happy in marriage then you have no right to seperate them, you cannot achieve anything forcefully.... Babies are out of hand and concent is alien concept for them. It's okay if their entire family gets totally destroyed, but Ushna should not live a happy life. That's it.