I can't remember exactly when my sister Cindy and I first began masturbating in front of each other, but by the time we were in high school, we would usually come home after our dates with other people and tell all about what Cindy called "the juicy details." My sister is a beautiful brunette with smallish-sized tits. I'd tell about dry humping my date in the front seat, or touching some girl's tits; and Cindy would sit back against the headboard of her bed and slowly bring her knees up, then open her thighs.
As she listened to me describe my sexual adventures, she'd moan a little, and begin rubbing her pussy through the thin cotton of her panties. While I watched, eventually she'd pull her panties off, let her skirt slide up to her hips and expose her naked pussy to me. By now my dick would be getting very nice and hard while I told what I'd done with other girls. Cindy would put her feet together, sole to sole, and spread open her legs so they formed a diamond shape with her pussy at the top.