Their Love

There is much speculation on their nature of the relationship between Haruka and Michiru.
In the American anime, Haruka says that they are cousins. (But Yanks are funny that in that they are afraid of close relationships) So here are some other explanations.

One theory is that Haruka is the Prince of Uranus, and was engaged to Michiru, the Princess of Neptune, during the Silver Millennium.
Since Senshi can only be female, Uranus, originally a male, was reborn a female, with her love for Neptune unbroken.

Another theory is that Neptune was engaged to Uranus's brother, and that Haruka and Michiru share a friendship, closer even, than that between sisters.

But they are, are lesbians, as is stated in the manga. So no, Haruka was never a man. They are lovers', destined to be together. Their sex is not a barrier, though Haruka is male in appearance, she is completely female in though and mind.

We are souls with bodies, not bodies with souls, thus, souls are attracted, no matter what the body is.

Click here for information in how Haruka & Michiru met.