@xianc78@matrixFWIW I've never heard of any guys actually being into it who had siblings to begin with. Nearly every time they do, they're an only child so they never had exposure to a sister to develop those natural "ew, she's not even a girl" instincts. A lot of fetishes are (often thankfully) like that, focusing on a non-existent, fantasized target that only really exists in theory.
Although I do have clips from the femcels talking about how they want their brothers. :?