It's Shining Armor's birthday, and Cadance has a special surprise lined up for him. But maybe not everything is quite as it seems.

Contains: Incest, not really incest, impregnation, not really impregnation, threesome, partner-sharing, voyeurism/cuckquean, changelings in disguise.
Cover art adapted from artwork by SugarlessPaints.
Written as an entry into the Mother's Day Incest is Wincest Contest. And yes, I asked about this one. It counts.