Stepsister from Planet Weird (2000)

Megan's life takes an unexpected turn when she learns that her tranquil existence with her little brother and single mother is about to be disrupted by a new stepfather and stepsister. Intrigued yet suspicious of their eccentric behavior, Megan resolves to sabotage the upcoming wedding. Her investigation soon reveals a shocking truth: her future family members aren't just odd—they hail from another planet. As she navigates this bizarre reality, Megan must confront her fears about change and the meaning of family.