[NSFW] Could a multi-gendered, gay threesome work?

TGIS question. At the Haymarket in Boston this Saturday, I noticed two very attractive women and a slender, epicene-looking guy; all seeming to have romantic interests in one another. Nothing publicly outrageous occurred. They were just hugging and holding hands—giving one another come hither glances.

But that brief encounter got me to thinking about settings of a more private and intimate sort, where the distance limits between the three were reduced till they disappeared, and some body parts began to merge. Who would do whom? What would they do? How would they merge?

If you imagined a household of three great looking gay adults, not all of the same gender, but all three relating sexually together, how would you imagine it working optimally? What pairing/s would you personally find hot and not? What mix of gender identities might help keep things steamy?

Does such a thing happen in the real world. After what I saw today, I am guessing it occasionally does. Pray do share life experiences to prove it happens if you have such.