For me, any female friend who wanted to know found out. Sometimes they asked, sometimes they grabbed it to feel it out, twice they followed me into a men's room to see for themselves, A few chose not to know. Only one of the times was a bit embarrassing.
My wife and I went on vacation with her brother and his wife. The brother was a year younger than me and often on the same sports teams as I was, so he'd seem my cock on many occasions and knew I was significantly bigger.
On the vacation, our villa had an outdoor hot tub. One evening, we ate on the patio, set up music and alcohol, and turned on the mood lighting for a nice lounge in the tub. We changed into swim suits, turned on the bubbles. and enjoyed the soak. Soon, my wife and I started to make out. Brother and his wife followed suit. Supposedly hidden by the bubbles, my wife started playing with my cock through my trunks.
After a bit, her brother asked, "Is what I think is going on really happening?"
I shrugged and admitted, "I'm hard."
Wifey dropped my trunks and pulled them off, tossing them to his wife. She blushed and ask, "Are you wearing underwear?"
I laugh and say, "Look under water if you want to."
Brother says, "Damn! I'm hard too, now."
Wifey takes matters into her hands and turns off the bubbles as she laughs. My boner can be seen be all.
Brother's wife's blush goes deep red. "Is it as big as it seems?"
"Bigger," my wife says.
"Bigger than mine," brother admits.
"Let's compare," my wife says, challenging her brother to drop his shorts. He does. "Both of you stand up. Face each other."
We do and the my wife puts our cocks side by side. I have the brother by about two inches. We play sword fight a bit.
"Can I touch them?" brother's wife asks.
"Sure," my wife gives permission.
She's still in a full body blush and stammers, "I ... I ... I haven't touched many."
"This isn't fair," I complain. "The dudes are naked and your still in suits."
"We can take care of that," my wife says, peeling off her two piece.
Brother's wife runs away.
By the time we traveled together again, she was let inhibited.