When my mum was expecting me, her brother (my late uncle) Barry took her for a burn on the back of his Beezer round the North Circular to the Ace Cafe (when it was merely a cafe and a rockers' hangout, before it became a franchise) and I reckon it got into my blood then.
My parents bought me a moped for my 16th birthday, as they did for my three younger brothers as well, a shrewd move to stem the incessant requests for lifts. Bikes were a passing phase for my brothers, none of them went further than a 125, though one, Mike, did pass his test when he was away at Uni as he'd learnt that he could drive a Plastic Pig with a full bike licence, and he couldn't afford to learn to drive at the time and he'd grown tired of the slog home to Northampton from Hatfield on his GP100 in Winter. The redoubtable Pig kept him warm and dry until he passed his car test. As far as I know, he only time he rode a big bike was when I gave him a go on my Genesis in 1988.