According to the story/update that I read, it is about this girl Zara... Zara has an elder sister called Zeenath, who is married to Aamir. They are very happy, except for the fact taht they do not have children... and Aamir has a younger brother Samar who has just returned from US. He would actually be Zara's classmate in the US and they both will be in love as well... when they want to tell the family that they want to get married, Zeenath asks Zara a promise... the story is about what Zara does in this scenario...
I just read this someplace... and this story reminds me of Jannath... a serial that used to come on DD.
Jannath is about this girl Jannath, who has an elder sister and brother in law... and the sister and brother in law are very much in love, but do not have children... sister. Jannath marries the Jeeja so taht she can give the sister a child... but sister misunderstands... in this melee Jannath loses her love, the guy she loved. finally elder sister becomes bad and keeps torturing Jannath... and seeing this, the jeeja falls in love with jannath... I don't remember the ending though!