Nella Swan <Volturi Kings>

In which Bella Swan has an aunt, four years older than her, whom she ends up dragging to Volterra via a phone call.

OR.

In which Delancy sleeps and wakes up in Twilight years before the plot starts. In her boredom, she accidentally becomes a global sensation.

Yet a day before her 16th birthday, she's surprised by a long and very late post letter informing her of the fact that she'll be coming into a sea based inheritance when she turns 16.

OR.

In which Charlie Swan has to deal with an adopted, mermaid-siren sister, twenty years younger than him.