People use both Haruki and Haruhiko, though the Japanese sites are more and more using the latter. They're also using Itsuki instead of Itsuko, except they they use different kanji (一樹 original Itsuki, 一姫 new Itsuki).
There's also a split on "Kyonko". Everyone uses Kyonko to refer to her, in English and Japanese, but in-story she's often just referred to as "Kyon". It's still just a nickname regardless of gender.