Gravity Falls BillDip: Traveling With You

Mabel and Bill are childhood friends. Mabel lived in Gravity Falls all of her life. Bill and her became friends after she freed him after Ford defeated him. Now
She is 17 years old, she only knows that Ford and Stanley is her family. She's also best friends with Wendy and Soos. One day, she finds out she actually has a twin Brother named Dipper.

Dipper has been living with his parents. He doesn't have much friends and hates being alone a lot. His parents leave him home alone a lot since they work all day. They want Dipper to become a scientist. Dipper studies all day and night, sometimes he wishes for a break or someone to calm him down. One day, home alone. He explores his attic that he could not go in, then he finds out that he actually got a sister named Mabel.

They had all sorts of questions. Most of all, why give up Mabel?!