Rehan was the only person who knew Tanveer's plan. He was the only one likely to alert Aahil. But we will never really know.
Up until yesterday, Aahil included, painted Sanam as a servant as well. So the fact Aahil has real feelings for Sanam, was news to Rehan as of yesterday. Rehan backed down, accordingly. He also respected that they were married and he admitted his faults to Aahil. The fact that Aahil said Rehan is like a brother and has constantly treated him like a servant was mean. No relationship should cost you your friend or brother. Aahil should have worked it out.
I know people thought Rehan was crossing a line, with the bedroom etc. But prior to Aahil calling Sanam his real wife, Rehan and Sanam were friends and they were always together and shared a comfort level. Who walks in the bedroom, when the door is open is for Aahil's mindset - not a big deal.
Rehan sees Sanam, again looking upset. She says I cannot find my locket, he helps her look. What should Rehan have done, let her fall... 😕
I do think it was good for Rehan to leave, he needs the space. I wish Aahil had been mature about it. I hope it was not the last we see of Rehan, he was engaging. I liked him and Aahil's dilemma. It never turned into the baseless circus going on at Faiz and Haya's place.