First of all, I love boobs, the bigger the better. I always jerk off to busty women on the internet. My parents know I jerk off, and they don't mind, and have caught me many times. In my home, it is normal to see anyone one, including me and my little 12-year-old sister, walking around naked after a shower to go and hang the towel up or something like that.
One day, when my sister was away on a trip with her friends, I was jerking off in my room looking at busty chicks on the net as I was holding one of my sister's bras, playing with it.
My mom walked by only in bra and panties because she had just left the shower and saw me through my open bedroom door. She came in, and asked what I had in my hand. I said it was Valerie's bra. My mom picked it up, and said, 'Your little sister has really nice breasts for a 12-year-old.' (Valerie's boobs are double C cup) I said: 'Yes she does, but nothing compared to yours.' My mom then took off her bra, and jokingly asked, 'Do you think I fit in Valerie's bra?' I just shrugged.
My mom then tried to put on my sister's bra as she was sitting on my bed. I was facing her, sitting on the computer chair, with my dick even harder than before. The bra was too small for my mom's E cup boobs, and it only covered her nipples, leaving the aereolas uncovered. I kept staring, and began to stroke my cock discretely, but my mom still saw it.
She then called me over to the bed, and I sat next to her. She began jerking me off as I played with her huge tits. When I told her I was about to cum, she got off the bed and stayed in front of me with her boobs right below my cock. I came all over her boobs and my sister's bra. My mom then asked me to take the bra off of her, and clean her breasts. As I did, I got hard by the time I was done licking my cum off her huge tits. She said that the bra would probably be stained, so she decided to keep it in her own closet for me to get it whenever I wanted to, and she would make up an excuse for Valerie once she got back home.