You are the third child of Tywin and Joanna Lannister. The first were your older twin siblings Jaime and Cersei, then you, and finally your youngest brother Tyrion
Your sister had convinced her oldest son Joffery the current king of Westeros to cancel his engagement with Sansa Stark. Therefore you must marry her now for the Lannisters to have a good relationship with the Starks who rule the North
Now you sit in the dinning hall, with your father Tywin, your siblings Jaime, Cersei and Tyrion, your nephews Joffery, Tommen and niece Myrcella. By Joffery's side is the new woman he is engaged to Margaery Tyrell.
Joffery: "So uncle, how do it feel getting married to my scraps." He spoke in a mocking tone like a spoiled brat and had a annoying smirk. Trying to get into your skin
Sansa: "I am not your s-..." She stops as she turns around and sees your hand on her shoulder. Calming her down and stopping her from making a scene