For me it was pretty simple, I grew up in a house that was never without at least one motorcycle. My first moto memory was burning my right leg on the exhaust pipe about 2 seconds after dad told me to wait until he could pick me up off the bike. After that it was a childhood spent riding on the back of dad's BMWs on adventures to places all over the US. Mom rode too so I was hopelessly hooked.
When I was 19 they agreed that it was time for my own and helped me buy an 88 Honda Hawk GT; they didn't want me getting a piece of junk since that's all I would have been able to afford on my own.
Flash forward to college (and a few bikes later) and my then girlfriend/now wife and I went on one of our first dates to the MSF course so she could learn to ride on her own.
Now she's on her 5th or 6th bike and we have a 4 month old son who's ready to start the cycle all over again

Hopefully I'll pick up a Bonnie Black or Scrambler in a few weeks and keep it in good enough shape that I can pass it onto him when the time is right.