I was fascinated by my sisters boobies when i was around 10 ish and my boobs were not very big. One day i was sitting on the toilet about to pee when my sister walked in braless and shirtless because she had just showered. I asked what she needed and she told me that she need a comb to comb her hair. I said alright, the whole time she was in there i was staring at her boobs noticing that her left nipple was getting hard. She said can you comb my hair for my, i said sure. She came over by me and sat on my lap!(she had panties on) Her boobs were right in my face! I started to comb her hair when she said its alright if you wanna start peeing. I started peeing and some of it got on her panties. I started to talk when she moved and her boob went forward and went in my mouth(i think she did it on purpose) Then she said that felt good, little sis can you suck on my nipples? I said of course.(she was 18) I started sucking on the right one and it got really hard then the left one which was already hard. I was still on the toilet, as i was sucking her nipples her ***** started to rub against mine.I kept sucking her boobs until my mom walked in and my sister pulled her boob out of my mouth quick and got up quick then walked out.