I've smoked weed with several of my friends parents, even smoking crack and taking percs with my best friends mom. I know my dad smokes, and his wife has a medical permit (Which gave her REALLY shitty weed) and a Sativex prescription, But they were generally dicks about my drug use when I lived with them, so toking with them would be out of the question.
Although several months ago my Mom was having a work party at her house, and came to me saying one of her coworkers was smoking a joint outside and I could join, but I think it would be just too fucking weird, as she was a correctional officer before, who had arrested previously stated crack smoking friends' mom.
But I regularly drink, smoke and do all sorts of drugs with my one older brother(+4 years), and have smoked with my oldest brother(+8 years). I also look forward to smoking with my little half-sister, who just turned 3, when she reaches a mature, responsible age.