Severus Snape has a twin sister Sarah Snape who's been left in the shadow of him there parents favorite Severus over anything in the world left in shadow she just goes with what she wants most of the time unoticed by her own brother but Lily Evans, Sirius Black, Remus Lupin and James Potter are there as well as some others but one day what she finds out by one of the boys while drunk from a marauder party changes her life forever (may have slow updates)