Stepsiblings Get Bored and Start Fooling Around Until Grandma Joins In
They hated being stuck at their stepgrandma's place with nothing to do so the stepsiblings started touching each other to pass the time. She walked in right as things heated up and instead of getting mad she decided to teach them both a lesson about keeping it in the family. Before long all three were exploring each other quietly making sure nobody outside heard what was happening.