Harry Potter baby sister

Harry Potter has a younger sister who was born a few months before her older brother and a little bit less then two years before her oldest brother . Yeah you heard it right harry has an older brother the same age as Fred and George. The oldest brother James jr or James for short was given to remus lupin his godfather Harry was with their uncle and aunt and aria which is short for Ariana was left on the doorsteps from the Weasley family. What happens hen the three meet eachother and find out they are brother and sister.