Tom and his Twin Sisters

I (Tom) was just turned 13 at the time when I was left at home with my older twin sisters Sophie and Kate who were 16.
Our parents had gone out for the evening and at about 9.30pm they phoned to say they had been invited by some friends to go on to a party and therefore wouldn`t be home until late the following day. They were quite happy to leave us alone as we were reasonably sensible (or so they thought) and could be trusted.
After a day of sports at a local club I was very tired and headed up for bed at about 10pm leaving my sisters downstairs watching television. I soon drifted off into a deep sleep. The girls meanwhile had switched over to the adult porn channel and were getting turned on by what they saw.
Although my sisters are twins, they are very different in character. Sophie is very outgoing and a born leader while Kate is much quieter and basically does anything her twin asks.
What happened next is only what I was later told as I was asleep at the time.
At about 1.30am the girls decided to head for bed in a somewhat excited mood after watching a porn film. They decided to check on me and quietly opened my bedroom door. It was a warm evening and I was wearing a tshirt and underpants and was lying on my back with just a sheet over me.
“He looks fine” said Kate. “I think we ought to check closer and see how deeply he is sleeping” said Sophie, knowing that once asleep I am a very heavy sleeper and it takes a lot to wake me.They walked over to the bed and slowly lifted the sheet. “what are you doing” asked Kate, “we are going to have some fun with our little brother” she replied.
Sophie lifted my tshirt above my chest and started slowly licking one of my nipples indicating to Kate to do the same to the other. “what if he wakes up, he could tell mum and dad” asked Kate. “don`t worry it would be his word against ours, and anyway he would be too embarrassed to say anything” Sophie replied.
They continued slowly licking my nipples then Sophie started running her tongue around my chest and stomach finally concentrating on the area around my belly button.