I ended up watching episode 11 again since i woke up earlier than usual, on a weekend. hehe. I figured I'll just back watch since I'm still waiting for complete subs for episode 13. I don't know, I may be thinking too much into the story, or I'm still looking for ways to justify Saran's actions in episode 11, but I realized something. Had the background in episode 12-1 been revealed earlier, then Saran would have been more forgivable. I think Saran gained most hates in episode 11 and 12 because of what he did to Rin.
For me, more than not standing up against Duang, I think what was more unforgivable was when Saran didn't hug Rin back when she hugged him in 11-7, after she said "we fell in love because of us, not because of who we are." I mean, I understand that plot-wise, had Saran stood up against Duang during the "big reveal" then the family or even Chalat won't have the chance to star in the scene and have their dramatic speeches. That was Chalat's crowning moment of awesome as all this time he's been shown as a sidekick to Saran at best, and he was a bit of a rich airhead who had a good heart. When he finally stood up for Rin and went all Papa bear on everyone, he suddenly looked like a man in charge - he's not spineless after all. the impact wouldn't have been as great if Saran stood up for Rin too - i think the context was, no matter what, Chalat would be on Rin's side as her big brother from now on. It also lays the basis for the concept "blood is thicker than water" - which would play an important part in the next episodes.
Anyway, back to Saran. Presumably, after episode 12-1, we'll know that apparently, it's not just Rin being rich that is bothering Saran. He's also bothered by the fact that she's a Rapeepun, the family that destroyed his family - and as Duang would later say in episode 12, Saran could bear being best friends with Chalat because they don't have to live with each other forever, but with Rin, they'll be one family. But of course by episode 11, we don't know that yet, so it's as if Saran is just being overly dramatic about it. But anyway, I realized when watching episode 11 after knowing the events of episode 12, Saran might have been thinking of his family too - all this time it was Rin who was putting her family first before anything else, and Saran was saying, no, I have to be your sun, you have to love me before anyone else, etc. But ultimately, family is family. blood is thicker than water. Saran is suddenly faced with a situation where he has to choose between the love of his life and his loyalty to his father - who supposedly died because of Rapeepun's actions. Rin cries "we fell in love because of us and not who we are" - but that's it, that's Saran's conflict. In his mind, because he is a Siwavhet, because he is his father's son, he cannot forget his father's death (and its relation to Rapeepun family). In the same manner, Rin is now a Rapeepun, she has a family with real blood ties - and again - blood is thicker than water. There is a dichotomy when Rin said "I choose you over Baranee because you're my family" - but that's it, Baranee, or Bumrung prachakit is not "What rin is" anymore - she's a "Rapeepun" and since Saran is faced with the same issue with his being a Siwavhet then he realized that who Rin is, or Rin's true family for that matter, is important. I think this whole family issue culminates with first, Saran's mother saying that when you marry someone, you also marry their family, which is true for Asian families. Marriage unites families. That's why I found Saran so immature when he was making Rin choose in episode 7 between her family and him - i mean, if Saran had to choose between his mother and Rin, wouldn't he be unable to decide out right (and perhaps he'll choose his mother too!) In the same way that when Saran learns that the woman he loves most is a daughter of the family who "killed" his dad, he couldn't let go of the issue just as easily. When Saran and Rin got married, they became one heart - and ultimately, they also became one family.
In episode 13, Saran was telling Rin to stay with her family, and do her duty. I think at this point Saran realized how stupid he was all along about the whole making-Rin-choose-between-him-and-her-family. That's what made him love Rin in the first place - her dedication to duty, her love for her family. In the same manner, he found himself being loyal to his duty too - that he would have to stop White Tiger for the good of the people, no matter what. But anyway, Saran was finally telling Rin to go! Be with your family! Do something that you like for once! Choose yourself! I don't have to be your sun, I don't deserve you, but know that YOU ARE MY SUN. So even when Rin was telling him that she was still the same old Rin, the Rin he fell in love with, he was insisting that no, you are Rin Rapeepun - that is who you are. You have a father, go be with your father. I can't steal you away from him (and in the same way, he knows she's torn to make a choice in the first place). Go be a princess. Be the best person you can be. Be a Rapeepun.
Hence the second culmination is in the ending when Saran finally decides that he doesn't give a damn, he'll be where Rin is, he'll love who Rin loves - he has forgiven/forgotten what the Rapeepun did to his father because the woman he loves is a Rapeepun. He'll love Rapeepun because Rin is a Rapeepun. Rin was like, no! I'll stay here with my dad! I'm done with your drama (about me choosing you over my family) - but then Saran is all like, yeah, I'm okay with that, I'll be where you are. I'll love who you love (Actually I haven't seen episode 14 with subs, but I'm assuming that's what they talked about in the ending) So with that I think it ends with Saran and Rin loving each other completely, falling in love with each other because of themselves, and also loving what they each are.