That is a very random question. And please don't take all of the answers and start trying to ask more about them, Guy. Like, if a person answers, don't start asking what her family member's bra size is or what her favorite lube is or if they would ever cam together or what her camname is. USE COMMON SENSE.
To answer the question, I've got a handful of siblings. 2 of my sisters know. 1 of them tried camming for a week, but hated it. Camming ruined her self-esteem, and ever since, she's been super hardcore working out/dieting and won't even talk to me about it. The other one was adamant that she will never cam (she thinks it's below her), but she has started asking me about sugardaddy sites and similar. My guess is that it's just a matter of time before she tries camming too.
And no, I would never cam with someone I know in person. Too many easy slip-ups (like real names/locations/etc).