A fairee tale

Arianna Morley is a normal girl 14 year old girl, with long black hair and silvery-grey eyes, but this story is not about her, it’s about Cassie. She's Arianna’s 7 minute younger identical twin. Cassie finds her older brother sneaking off and one day she starts to follow him, this decision changes her life but can she keep her, her brothers and maybe a whole other worlds secret from her twin/best friend?