The younger sibling, their eyes filled with curiosity and lust, watches as their elder sibling prepares the lubricated toy, a promise of the forbidden pleasure to come. The elder, with a confident smirk, pushes the toy against the younger's virgin ass, feeling the tight resistance give way as they slowly slide it in. The younger's breath hitches, their body tensing, but as the elder begins to move the toy in and out, they relax, moaning softly, their eyes rolling back in pleasure. The elder, watching the younger squirm in delight, knows they've found a new, taboo source of pleasure.