My uncle used to take me to the field house to lift weights the summer before his senior year when I was like 7 years old.
He was always one of the strongest dudes on the team and as a young fella you look up to guys like that in your family.
Of course, I didn't start lifting til a few years later, but looking back that was probably the first seed that was laid.
I had another Uncle that started lifting when he was a young teen and still does (he is like 49 now, looks great). He always had a pretty decent home gym set up. Usually a converted shed that contained a bench, squat stands (not the power rack), a few different shaped barbells and a loadable dumbbell handles, and probably around 800 lbs or so of weights.
I guess when I was about 12 or so, I asked him if I could borrow some of his weights and he said yes. So for the next couple days I would bike the 2 miles to his house and load up my back pack with some plates (I already had a bench and bar) and bike back until I had about 150 pounds or so......went back home and started busting out curls with the little standard bar and a couple piss small "screw on" plates on the side.