Well, half-brothers and half-sisters are not related at all, so it can't be considered something bad or immoral. It's no surprise that an adult guy and girl, with no regular sexual partners and almost daily being around each other, suddenly felt attracted on a sexual level to each other. Considering that the girl liked it (the guy then no question), I think they will continue to practice this kind of thing from time to time.
For a long time I wanted to find out what is so unusual about call girls, once they have a huge demand for their services. Now I understand, a rare girl will be so long, skillfully and with such pleasure to suck her boyfriend's dick. A minute, two minutes, and then be good to switch to her pussy. She'd give a blowjob until you pulled her hair out! She's definitely worth her money.
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