Another who was born to nerdhood here. It was definitely a collaborative effort to nurture it, though.
My maternal grandmother loved fantasy; when I was little, every summer either she and my grandfather would come to Seattle to visit us, or I would go to Philadelphia to visit them. Every summer we read another Oz book (or two) together; the summer she had laryngitis and she couldn't read to me, little-me worked hard to read the book to her instead because the tradition was that important to me. She was a physicist, chemist, and engineer, and the one who got me interested in computers and my start in programming. (She's also where I get much of my life philosophy from; nerdiness aside, she was absolutely the single biggest influence on my personality.)
My dad is a science fiction fan; when he realized I was reading way ahead of my grade level, he gave me Downbelow Station and The Pride of Chanur to read (C.J. Cherryh is one of his favorite authors, even still today). From there I went to get more Cherryh books (the Faded Sun trilogy) from the library and stumbled into Clarke, Asimov, Silverberg, and other old classics they had on the shelves.
As I kept reading voraciously, I started to give dad recommendations in return. When that happened, dad set aside a shelf in the house where we would collect science fiction and fantasy books which we both agreed were true classics; all my life, that shelf has been slowly filling as we read something and both agree it should be added. The first thing we added was dad's beloved Downbelow Station; the second, which I nominated, was Vonda N. McIntyre's Dreamsnake.
(...which I'm suddenly finding leaves me on the verge of tears to write. Years later I met Vonda and she became a friend, a mentor who took meâand many othersâunder her wing. For fifteen years she's been someone who I could turn to for advice about writing, or life, or even just to swap book recommendations. She also pulled me into a lot of activities, and I owe no small part of the offline fandom aspect of my present-day nerdiness to her. But I stupidly let myself get wrapped up in work and other things over the past year or so, letting our lunch dates become much more infrequent. It always felt like there would be more time later, until suddenly there wasn't any left at all, and her death this past Monday is still a fresh wound. Treasure the time you have with the people you care about, folks; it is not limitless. But I digress.)
My mother was not a huge science fiction and fantasy reader, but she was a Star Trek devotee; she pulled the rest of the family into watching The Next Generation every week with her, and from there I fell into the X-Files, Space: Above and Beyond (it was a great show shut up), and Babylon 5.
My maternal uncle was also a huge science fiction fan, and when he saw that I was reading classic science fiction, he introduced me to his frankly intimidating collection of old issues of Astounding, Amazing Stories, and Asimov's stored at my grandparents' house; I only ever worked through a tiny fraction of them when I'd visit Philly, but he's why I still have a (digital) subscription to Asimov's today. He also introduced me to Dan Simmons' Hyperion Chronicles, one of his favorite series. And, relevant to this forum, he was a D&D fan and introduced little-me to the idea of roleplaying.
My maternal aunt, meanwhile, is an enormous Tolkien fan; she is how I was introduced to the tapestry of stories in Arda. First the Hobbit, the the Lord of the Rings, and finally the Silmarillion
It wasn't just my family either, of course. My friend who lived across the street from me introduced me to Star Blazers, thus showing me that animated shows could have actual narrative arcs instead of being purely episodic. And little-me's best friend had a Nintendo; pleading to go visit even so I could just watch him play, if not play myself, was my first introduction to games. (And arguably, I suppose, to the concept of Twitch.)
So, yeah; my nerdiness was a team effort.