My Husband Is My Twin Sister's Fiance

Sherra Alchemy is an orphan who got adopted by the Harlock Family. Sherra Alchemy has an identical beautiful twin sister, and her name is Sherry Alchemy.
Sherra and Sherry lost their parents in an accident, and they didn't have any other family besides their parents. A kind grandfather came and picked them up, and the grandfather adopted them to be his granddaughter.
He is Mr. Harlock, who already retired from his job as the company CEO. Mr. Harlock always treated Sherra and Sherry as his biological granddaughters.
Gerald Harlock is Mr. Harlock's biological grandson from his older son. Mr. Harlock treated Sherra, Sherry, and Gerald with the same treatment. Gerald is older than Sherra & Sherry.
Every day was a sunny day when they played together like any other normal siblings out there. Everything changed when Gerald started to love Sherry, Sherra's twin sister, and Sherra also had the same feelings as Gerald.
Sherry and Gerald didn't know that Sherra also had some feelings towards Gerald. Sherra decided to bury her love deep down, and she would support her twin sister's love.
Their peaceful day ended when Sherry got an incurable illness and died because of it. Gerad was really angry at Sherra when he found out she had deliberately let Sherry die.
Gerald didn't know what truly happened, but he blamed Sherra for the death of Sherry. Gerald already knew that Sherra had feelings towards him, but he always turned a blind eye because he only loved Sherry.
Mr. Harlock forced Gerald to marry Sherra after two years of Sherry's death. Gerald didn't have any choice but to get married to Sherra.
"You won't ever get my heart forever," Gerald said with a cold gaze towards Sherra.
Sherra's heart broke into pieces after she tried hard to make Gerald fall in love with her. Sherra left Gerald after she gave birth to their twin sons.
When Gerald found out that he started to open his heart for Sherra, Sherra already left him with their twin sons behind. Gerald finally found out the mystery behind Sherry's death but Sherra is nowhere to be found.
[ DISCLAIMER: the picture in the cover is not mine, credit to the owner! :) ]