Angel's Nightmare

Skylar and Angel are descended from a family of werewolf shapeshifters. Their older sisters Raven, Lyca, Harley and thier brother Tyler all came into the gene when they were too young to remember, but it seems to have skipped over Angel and Skylar, much to their annoyance (Angel's more so than Skylar's.).
Over the past little while they appear to have changed, with constant mood swings and angry outbursts. And there's one question on everyone's lips: What's causing it?.