Both characters in this story are over eighteen.
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Alex walked up the hill towards his older sister's house. He and Heather had always been close, even though they didn't see each other that often, but it had recently gotten awkward for him. He'd started to remember when he was younger, and he would peep on her. It definitely wasn't curiosity; he felt a sexual attraction toward her. He now realized these feelings had never really died, but it was more than that. Heather had basically become his image of female perfection. Everything he found sexy in women, even the little things, all went back to her.
Fortunately, any time they'd gotten together since then, he'd had no problem acting normal. He walked up to her front door and rang the bell. It took about a minute or so for her to get there. Heather was, to put it simply, a BBW. She was a little larger than when she was younger, but still very attractive. Her attire on this day suggested she was still getting dressed for their lunch out.
"Alex, you're early. Well, come in." He came in, closing the door behind him, and followed his sister to her room. Heather didn't mind changing in front of her brother. Even though he used to peep on her, she figured that was just a phase, and he had no real desire to see her like that, and would just look away. After all, she was his sister. It was the same way for her; she'd always had a thing for big guys, and Alex was definitely big, a clear foot taller than her. But she'd never connected the two, because he was her brother, and you just don't have those kinds of thoughts about your brother. Right?
Heather took off her t-shirt, and Alex's heart immediately began racing. Ordinarily, he would look away, but now, he felt compelled to stare, as his sister went to her closet to pick out a fresh shirt. Some inner force was trying to push him forwards. He knew if he did what he was starting to think of, it couldn't end well.
Heather was about to pull out a blouse, when she felt her brother's hand on her shoulder, and her heart started pounding. "Alex, what are you-" She stopped, as her brother started rubbing her shoulder, then she felt his other hand on her arm. What really made her gasp, though, was when she felt his lips on her shoulders and neck. This caused her nipples to harden, and her pussy to moisten. "Ohh...Alex..." She involuntarily pushed her huge, soft ass into him, and felt his big, hard cock push back. Heather didn't know what had gotten into her brother, but she knew it was all kinds of wrong, and she knew she didn't want him to stop.