Half-sister...

After banging her hands on the door for a long time, Yan Ruomin became numb and went to her bed. When going there she turned off the lights of the room in a semi-conscious state beside the bed and became unconscious as she dropped on the bed on her back. While the white tiled floor had many bloody marks on it which could take people's souls away. The blood didn't stop following till then.

...

Su Mengsi had married someone before she married Yan Luhan's father. Due to some unknown reason, Yan Ruomin's father died when her mother was one month pregnant with her. 

After that, the Su family remarried her mother away to the Yan family because Yan Luhan's father promised to give Su Mengsi's brother some benefits if they could make her willing to marry him.