The shooting is clearly amateur, the lady doesn't want to advertise herself and is wearing huge glasses all the time. Is she skinny? I would rather say she is athletic with a very nice figure. It's a pity they fuck in such unsanitary conditions. If they would have taken a hotel room, they could have made a more interesting video.
I must say the lady is very experienced - her front is developed to the limit! Too bad she sucks so little - she clearly does it professionally! When the cock falls into such an experienced mouth you want the lady to suck it to the peak and swallow the cum. And then, when your pleasure was just off the scale, she continued to suck his cock slowly and tightly! And then, after a little break, it's nice to put the lady in the cunt and slowly fuck her for a long time!
Now that's what I call a real brother-sister relationship - they're a team! And they were foolishly burned, because the sister at the end asked aloud if he came inside her. And so - all the movements are honed and memorized - it is obvious that they do it not the first time.