I haven't played the game yet, but there are some new guides online, and the recent info looks consistent. So:
Human females are Piper and Cait.
Nonhuman female is Curie, a Miss Handy robot.
Human males are Preston, Danse, and MacCready. (Initially one of the devs, Todd Howard I think, said all humans would be romanceable. Apparently this is not the case since Deacon is not.)
Nonhuman male is the ghoul Hancock.
You can romance all of them with either gender, and apparently you can romance more than one at a time without repercussions. Though I wonder if this is true for all of them (Jim Sterling of Jimquisition romanced Cait and Hancock at the same time, IIRC).