This story is a sequel to Awaiting her Title
Ever since Twilight Sparkle gained her cutie mark, a particularly magical event that she still barely remembers, a small scribble has been barely visible on her fetlock. A First Words Soulmate Mark. As time marched on, those very words ever so slowly became clearer. It is on the eve of her big brother's wedding that she hears those words spoken... by his fiance.
But that should be impossible, right? His fiance was her childhood foalsitter, wasn't she? Twilight has clear memories of their time together. Plus, wasn't Cadance already her brother's soulmate? She'd never heard of one pony having multiple soulmates before. On top of all that, the first words she had heard from Cadance absolutely weren't a coldly delivered "Hope I'm not interrupting anything important." This needs to be investigated...