In the series, Alona and Perlas are born with unusual features—one is born with gills behind her ears and the other with a mermaid's tail. Worried that neighbors might be surprised by their strange features, their mother decides to move along with them to an isolated island. Due to unfortunate circumstances, Alona and Perlas have to live separately. Living with her mother, Perlas works in an ocean park while Alona lives as a princess within the confines of the waters—the kingdom of Sirenadia.
Kevin is a handsome and rich son of Susanna , whom the twins fall in love with. Kevin manages the family company where he meets Perlas. As they start to develop feelings for each other, Susana learns that Perlas is the daughter of Marissa, who they consider as the cause of her brother Enrique's death. Meanwhile, Alona also finds love with Kevin specifically when she was able to save him from drowning.
Two individuals with different personalities and circumstances fighting for one man. Who will win the heart of Kevin? Will the uniqueness in Alona and Perlas be a hindrance for them to be loved?
—————
https://www.gmanetwork.com/entertainment/tv/kambalsirena/about/