It looks very unpleasant - a well-pumped guy is trying his best, and the lady's face is covered with a strange grimace. In general it is not clear - whether she enjoys sex or performs an unpleasant duty! And the body of the lady is not particularly that glitters, and her breasts and nothing at all!
Teasing her brother with her pussy, her fingers wet with juices, manipulating his brain and his purple head is such a turn-on for girls. It's easier for them to suck his dick or get cancerous than to give up this kind of fun.