I always have and always will fantasize about my older sister giving me a handjob/blowjob and fondling my balls.
The other thing (similar though) is that once when I was feeling down (for a few reasons) she let me sleep in her bed with her. When she fell asleep I gently played with her tits. If I hadn't been afraid of her waking up, I would have probably buried under the covers and licked/sucked her feet too.