I Will Divorce the Female Lead's Siscon Brother is a Manga/Manhwa/Manhua in english language, Drama series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Ethel, who reincarnated into her favorite novel, has married the female lead’s brother Liena. She thought her marriage life was genuine, but soon enough she became tired of a husband who cared only for his sister and whose attention was always centered on Liena, yet was cold to her, so she filed for divorce. “Divorce? Absolutely not!” However, her opponent is a powerful duke, so she turns to Terrence, the villain of the original story to be her assistant for a smooth divorce. “The only person I want to have by my side is you, Ethel.” …But this man’s fate is to be hurt by Liena. As the more she knew about Terrence, the more he seemed attractive to her?