I recommend Flash Marriage Love: Paranoid Husband Addicts to You. In order to save her younger brother, the female protagonist took the blame for her half-sister. The male protagonist thought that the female protagonist was interested in him and confessed to her. In order to protect her younger brother, the female protagonist had to marry the male protagonist. After marriage, the male protagonist doted on the female protagonist, but the female protagonist found out that the male protagonist's brother was her own brother. Facing this fact, the female protagonist began a complicated emotional entanglement. I hope you like my recommendation. Muah~