Cadance was a pegasus born to two earth ponies (we know this is possible from Pound and Pumpkin). The ponies still held prejudice against other races even though peace was declared among the ponies many years ago. They raised her up until she was 14. They mistreated her and Cadance never felt loved. They orphaned her on the edge of a forest near Canterlot. She survived two whole nights before being found by Celestia. Celestia took her in as her niece. For the first time in 14 years, Cadance felt love and acceptance. She realised how important love was to all ponies and learned to sympathize with and help others who never felt love. Then, her cutiemark appeared. Celestia realized how special she was and took her under her wing and trained her for……..alicornhood?