In the "How We Celebrated Our Sister's Birthday" video, Ranz and Niana document the special day they planned for their sister. They share the preparations, including decorations, food, and thoughtful gifts, all aimed at making her feel loved and appreciated. The video captures joyful moments, surprise elements, and heartfelt messages as they celebrate together with family and friends. Their playful interactions and genuine excitement create a warm atmosphere, showcasing the importance of family and the joy of celebrating milestones together.