Listen, Sister Sue!
Men don't say much because women have all the power, unless everyone is buying into some sort of nonsensical fundamentalist paradigm. If the national culture weren't so sex negative that an alien onlooker might consider immaculate conception to be plausible, at least in the U.S., then guys would still be willing, humbly and worshipfully, to ask. The most incredible force in the universe is female orgasmic energy. That, and that alone, is what every man looks for and longs for(although quite a few are so ignorant that they THINK they're trying to get their own rocks off). I've written a screenplay based loosely on the ancient Greek story, Lysistrada, which is the prototypical gender genre yarn for twenty first century America.
As to your bro's friend, unless your brother is TOTALLY OPPOSITE YOU, he's probably wondering why you and his bud haven't gotten it on already. And the fellow himself fears offending you---many women are TOTALLY fucked up about commitment and such, believing that their conceiving of sex as sacred somehow gets rid of the blood and carnal lust of the act---and, like you say, is so HOT that he's well-satisfied(never satiated, mind you, but for a moment or two), and so glories in the energy you share together. If, as makes sense, your brother is a cool guy, just ask the friend to meet you for coffee sometime when you have a few hours, and everything else will take care of itself. If for some reason your brother feels insecure about his friend consummating lust with you, then DO WHAT YOU DO HERE, SILLY GOOSE!! Write him a note explaining everything, and how you want to be his secret 'friend', a special treat that both of you can remember for all your days.
Just make sure you do plenty of yoga and stretching beforehand, as you'll obviously need it. YUMMMMMM!!!! BTW, I'll be your special friend, if there's any chemistry between us. I have always liked women who were rational AND hot about sex; it's the only way that works, in the scheme of human history, what with there only being one thing certain and all. Good luck, and
Ciao for now,
Jimbo