I've known I was poly...since before the word was invented (in 1990, according to Wikipedia). I started reading Heinlein at a very young age (12 or so). Many of my views on sex and relationships were/are quite obviously Heinlein influenced. Before I met MrS, I was pretty much of the opinion that I wanted to have sex with whomever I wanted and loving friends and FWB but had no interest in the types of "relationships" modeled by my peers (and society at large)...then MrS happened and I eventually had to acknowledge that such a thing as "romantic love" actually existed...so I had to fit that in as well. 19 years later the miracle happened again, quite unlooked-for, and now we have Dude as well, all nestled in there...apparently these things just happen sometimes.
(I'm working on the longer version in my blog - 8 big posts and I am up to 16 years ago...)