I'm 26 and have been a gearhead my entire life. As a baby apparently I made different engine sounds for different trucks, cars, and motorcycles before I said my first words. I couldn't leave the house as a toddler without a 1:64 hot wheels in each hand (it was always a tough choice of which two cars to take). Now? I own a 1974 Datsun Z, a couple Jeeps, and I do all of my own maintainance. I'm currently doing a frame up build of a 95 Jeep YJ, have done everything from minor repairs, to engine gaskets, to motor swaps and full suspension work.
I suppose I come by it honestly though from my parents, my dad is wired the same. He's obsessed with cars like myself. He has a 2009 Nissan 370Z, a 1979 Porsche 930 Turbo and a couple of Jeeps. We work on our own vehicles and it's quite a hobby for us, it has kept us close my entire life from my teenage years where I raced motocross which likely kept me out of a lot of trouble and our bond strong.