Your girlfriend's oblivious sister

You thought you'd struck gold when you hooked up with your girlfriend Caitlin. Unlike your previous girlfriend you broke up with just months ago, Caitlin had firm D-cup breasts and great looks overall. You have always been a boob guy, but you lacked the self confidence to actively approach busty girls. Now you were lucky that a busty girl with a fun personality took the initiative and was now dating you. Life was good. But as they say, there's always a bigger fish.

As your relationship was starting to get serious, you got to meet the parents and finally the sister of your girlfriend, Dana. You got to see her occasionally when you were both visiting the parents of the two girls, who all lived in different parts of the country. Physically, Dana was an improved version of Caitlin. The first time you her she was wearing a baggy sweater, but you could see she had bigger breasts than Caitlin. She was slimmer, bustier and better looking than Caitlin. This became obvious when you first saw her at the girls' parent's place. She was wearing much more tightly fitting clothing when she was with her family and you. In fact, there was no trace of her normal inhibition in public situation. It didn't seem like she was trying to show off her incredible body, it seemed more like she was completely oblivious to the kind of signal a curvy female body sends to a healthy male looking at it. The only thing that kept you from thinking you had picked the wrong sister was the fact that Dana was not the kind of fun and kind person Caitlin was. You could say she was a bit of an asshole most of the time. Dana only acted like a jerk towards her family members, she was always kind towards you.

Dana seemed like a prude compared to her sister. She would just roll her eyes at any dirty jokes Caitlin dropped on a regular basis. You got the impression that she had never had any serious relationships with anyone. This restrained manner contrasted with her body of a porn star and her inability to keep it hidden in family situations would eventually drive you nuts. Dana could emerge from the shower wearing just her bra and panties, then go change into her night gown, which she should have ditched for a bigger size years ago. The night gown was the opposite of baggy, hugging her natural breasts and letting her nipples stand out through the fabric. She would leave her bras lying about haphazardly, and one of your favorite parts of visiting the girl's parents was to study Dana's bras. This is how you learned she wore 34E bras, whereas Caitlin was "only" a 36D.

You even managed to get a full view of Dana's breasts one time. You went to the kitchen to get a glass of water and casually glanced at the next room, which in turn led to the bathroom. You realized Dana had not only left the bathroom door open, but also the door between the next room and the kitchen. You could see Dana in her full naked glory, water running down her incredible bosom. Her nipples were pointing slightly upwards despite their incredible size. Starting from that visit, you would sneak off somewhere private and jerk off whenever you had witnessed one of Dana's little strip shows.

As the years went on, you realized you hadn't even seen the best of Dana when you first got to know her. As she got older, she gained weight in just the right places and transformed from slim with big breasts to chubby with gigantic breasts. The growth was easy to follow as you could check her growing bra size from the bras that Dana kept leaving around.

One summer, you went on another visit on a particularly hot day. The two sisters are also completely different in that Dana always complains how cold it is, whereas Caitlin hates the sun. The girls' parents had just left the house to do some shopping. Dana said she would go to the backyard to catch some rays, while Caitlin said she would rather stay inside. Now, you usually hate the sun as much as Caitlin, but at this particular time you chose to join Dana on the backyard. Dana was lying on her back on the patio in a bikini, and you sat in a lawn chair next to her. You could clearly tell her breasts were again slightly bigger than the last time you saw her. You sat with Dana, chatting idly with her while soaking in her incredible bra size. You grew harder and harder, almost compelled to touch yourself in Dana's presence. You excused yourself to go the toilet. There was no sign of Caitlin, so you assumed her to be in another part of the house. On the way to the toilet you went to Dana's old room where you assume she changed to the bikini. Just as you expected, you found Dana's bra lying on her bed. You picked up the bra and noticed she now needed the cup size 36G. Your cock jumped a little more when you read the size marking in the bra. You took the bra and headed towards the toilet. You pressed the door handle. Clunk. Locked from the inside. You heard the voice of Caitlin inside: "Hang on, honey, I'm taking a dump!" You turned around to quickly take the bra back, but you realize Dana is inside and she already witnessed you heading towards the toilet with her bra in hand. "What are you doing? Were you going to jerk off in my bra?", she demands. You were struck by panic. To your big surprise, Dana broke into a smile and started undressing from her bikini top, saying: "Wouldn't you rather fuck the things I keep in that bra?" She let the bikini top fall on the floor, revealing her natural G cup breasts that had started sagging a bit since you last saw them naked, but they were nonetheless an incredible sight. At that point you heard the toilet door open behind you. You panicked even more when you realized Caitlin had heard everything her sister said. To your surprise, Caitlin was also smiling. "It's okay, honey. Have some fun with her. I know you want to. I'll go for a walk and leave you two alone."