I accidentally sucked my sister’s clit, thinking she was my girlfriend. I was 20. My girlfriend was supposed to be waiting in my room in the dark. I came in half-drunk, saw a girl under the sheets, and crawled between her legs without turning on the light. I yanked her panties to the side and put my mouth straight on her. She was already soaked. I licked her slow at first, tongue dragging through her folds, then sucked her clit hard the way my girlfriend liked it. She moaned soft, breathy and grabbed my hair. I kept going, tongue circling, sucking harder, messy and wet, until she started shaking.