Not knowing that their lives are intertwined, fate brings together the underprivileged Celyn (Kim Chiu) and the rich Margaux (Maja Salvador). They become the best of friends until the truth is revealed and becomes the fuel for their rivalry. To make things worse, Celyn's friendship and fondness with Liam (Xian Lim) and Ethan (Enchong Dee) magnify Margaux's insecurity, making the latter vengeful against her former best friend.

Ina Kapatid Anak tells the story of Celyn (Chiu) and Margaux (Salvador), two different women who grew up living two very different lives. Celyn was raised in an impoverished family in a province, while Margaux had the life of a princess as the heiress of the country’s biggest shoe company.

They are fated to become the best of friends but only until a well-kept secret from the past is revealed—Celyn is Margaux’s adoptive parents long lost daughter through a surrogate that took her away. Rivalry ensues between the two and they will fight over everything from status, to family, and even love.

Ina Kapatid Anak is a compelling story about family, love, power, rivalry and acceptance. It featured a powerhouse cast composed of Kim, Xian, Enchong, and Maja; highly-acclaimed seasoned actors Janice de Belen, Cherry Pie Picache and Ariel Rivera; and well respected veteran stars Ronaldo Valdez, Pilar Pilapil and Eddie Guiterrez, under the direction of Don Cuaresma and Jojo Saguin.