My sister came to my brother to keep warm at night and somehow everything happened itself

Late at night, the girl woke up from a terrible cold in her room. He decided that he could not warm up herself and decided to jump into bed to his brother. Bad thoughts on the sleepy head and somehow everything happened itself. A few minutes and they were already fucked in full, despite the related bonds. And sex turned out to be so passionate, as if they were lovers. And warmed up and had sex in one!