Princess Cadance

Princess Cadance is a Pegasus unicorn pony who is first featured in the season two finale A Canterlot Wedding - Part 1, alongside Shining Armor, her husband-to-be. She is the former foal-sitter of Twilight Sparkle as shown in a flashback, and becomes Twilight's sister-in-law after the marriage of herself and Shining Armor in A Canterlot Wedding - Part 2. Various promotional materials, including a  New York Times  ad[2 ] and official episode summaries, state that she is the niece of Princess Celestia