washing my s****rs back

When I was 16, my s****r had just gone into the Air f***e. A few years older than me we had allways got on. I remember her first visit back home after 3 months. Phisicly she had changed she was more toned, and was looking Hot. she wore a short summer dress when we picked her up at the station. It was a hot summers day & our parents drove us back to our house before they were heading off to a evening dinner with friends. Leaving my s****r & I at home, we were chatting away catching up on things when I got down to my boxers due to the heat & she decided she wanted a shower to cool down & refresh. we had moved our conversation up stairs as she prepared for her shower. Wow she was looking Hot & more to the point undressing before my eyes, her body was tanned & now well toned. her breasts were a pert 34b & looking delicious as she raised her arms to tie back her hair. I suggested i leave her to it & go down stairs, she said for me to stay & continue to chat. She closed the shower curtain and we were chatting about old times & the past when i noticed her dress & undies on the floor. I pick them up in mid conversation & took a deep breath as i could smell her sweetness. I was getting hard & could not only smell her but could also see her faintly through the shower curtain. I started to masturbate while i watched her i can see she is washing her hair & is all lathered up with her eyes closed so i take a better look & pull the curtain to one side, Her bum looks so soft & juicy the water cascading over her buttox my cock throbbing with happines she quickly turns with one eye open & says can you pass me the face cloth. she puts the face cloth over her eyes with her head facing up & calmly askes can you wash my back please..... Oh im in heaven I get the soap & rub the soap into her back, my cock poking through my boxers eagerly watching her breasts & Bum & pussy as my hands glide over her lovely hot body. my cock now dripping with pre-cum I take some from the end of my cock & start to massage it into her back with the soap. your good at this she says, how do you mannage to get the soap so creamy.......... Hmmmmm Im not sure if i should tell her.