Also regular fluid

Root¹ of androgynous is andro(masculine) gyn (feminine) ¹guess which language?

Mawage. Mawage is wot bwings us togeder tooday. Mawage, that bwessed awangment, that dweam wifin a dweam... And wuv, tru wuv, will fowow you foweva... So tweasure your wuv.

It seems pretty simple to me. A changeling couple is....a couple. No more labels needed.

In gay mating, which penis expands to be receptive to the other penis?

Not necessarily!

It's interesting being a genderfluid person married to a woman. Sometimes she is straight and sometimes she is a lesbian. We are both always bisexual

Closer to genderfluid

Cis people trying to decipher all the types of gay 

Their planet didn't look like it had much for seasons. Or even environments lol

We've got a British one, which I think explains a lot