That's the kind of slutty sister every brother would let work his testicles. And this one probably accustomed her to these pranks a long time ago. At least that's what I would have done. She'd have to suck and spread her legs anyway, so why not with her own man? It's about time she got her ass printed, too, so she can date like a grown-up bitch. Or maybe she's still trying to keep her anal virginity for her husband.
Girls just shy away from sucking at first. Once they give a blowjob, all their embarrassment disappears. They begin to work on the technique of moving the hands, taking the cheek, dipping deeper and deeper into the throat. If the cock is not too long, they try to take it all in their mouth, to get their nose against the man's pubis. A little alcohol and she can already suck your friend's dick. It's a nice feeling when you mold a modest girl into a real bitch. Now for her to take cum in her mouth and swallow it becomes the norm. Gradually you get to her ass. After that, she no longer cringes if you treat her in bed as an available woman. It even turns her on.
That's a great massage. It's even hot.