Always had a fantasy about my SIL always thought she was hot always wanted to know how she would be in bed is she shaved or natural pussy tight or loose always have thoughts and jerked many loads to her
While it is possible, I've no certain knowledge of it.
I have a middle brother, close in age, where we're often mistaken as twins. KK's had a fantasy since we've started dating, centering on being in an MFM threesome with the two of us. He's seen us fucking at least twice I know of, once barging in on us during our dating years, when we thought we had the house to ourselves, a second time in between semesters at college, similar circumstances.
We've done the pillow-talk / role-play thing on the topic dozens of times - she gets off to a smashing orgasm every single time.
All that said, I don't know that she's ever fucked him, and to the best of my knowledge he's never made an advance on her - certainly not one I've witnessed.