My partner, a cis-gender male knew from the beginning that I identified differently (gender-wise) than most biological women. He was quite ignorant to knowing things about Trans-gender people. I do not believe it was from lack of caring or understanding (he understood very well when I started to tell him) it was mostly that he had never known anyone who was TG and in his country there is less emphasis on a clear line between the binaries and more acceptance for LGBT people.
He was a little uneasy at first, since he identifies as heterosexual (though a short time back he was thinking about it and out of the blue said to me "maybe I should say I'm hetero-flexible, since I'm with you?"). I was kind of flabbergasted because that makes me feel like he's really in for the "long haul". He says a lot about "Someday when you start taking hormones..." or "If you decided to get this surgery or that one" and then he will ask some sort of hormone or surgery related question.
We've been together for almost 2 years now, and while it's a long-distance relationship, I'm insanely happy even with the few ups and downs we've had along the way. I'm not sure if he was ever this open-minded before we met but I think that meeting me has really done a great deal for him, he's been opened to so many things he never would have known or had anything to do with if he hadn't met me.