Any chick loves it when her pussy is licked. And this brunette found a loose tongue from her brother. Naturally, for such services she had to pay the full price - to take in her mouth and let her slit put on his dick. I can only see that she enjoyed it. And to feel like an actress being filmed and licking at the sight of her vagina and cum on her lips - she just enjoys it.
They did a good job, but I doubt if any of the guys are the lady's husbands! As a last resort, if the lady needs two guns at once, she can buy a toy. But to let the second man come to his wife, I think it is very inconsiderate!