Kahin Toh Milnge was story about four siblings who were adopted by 4 people. Two went in rich family while two in middle class family. The rich one bonded with each other & vice versa. The girl who was from middle class family falls for a rich & a simply guy (Shashank) but sacrifices her love for her sister when she finds out she is her sister & loves the same guy.
Shashank marries younger sister. Elder sister marries her boss who is later on killed & she is sentenced for the crime. The show takes a leap. Elder sister is back with a new identity, face to take revenge from her own people. Later on it is revealed that Shashank who is her sister husband whom she once loved & trusted alot killed her husband.
The rich brother was played by guy who played role of Samman earlier in Ghar Ek Sapna, rich sister Karishma Tanna, other sister female who played Anurag's second wife in KZK, other brother by goon who had tried to kidnap Ranbir-Rano in the jungle in the show Ranbir Rano while the sister whose husband was killed his role was played by Aryaman of Kkusum fame.