I have no idea if anyone tried this yet.
Elementals are taught all their lives to abide the laws of nature, in other words: stick to their own kind. Fire with fire, air with air, water with water, and so on.
This was taken very seriously, and all elementals were devout to this rule, well most of them.
Flame Prince was taught all his life that fire's purpose is to burn and destroy.
Fire was vulnerable towards water, and making contact with it always resulted in disastor. He knew this, and yet, lately he had been having these thoughts, these...fantasies...of a certain Water Princess. Asleep during the night, or during daydreams in the day, Flame Prince had these constant visions about this girl of the water.
Normally he would never think twice about making contact with an opposite elemental, but for some reason, this girl of the opposite element was burned into his mind.
Flame Prince tried to rationalize these feelings, thinking, maybe Water Princess was a siren or a witch, trying to draw him in for whatever reason, or, he thought, perhaps he was sick and his mind was messing with him.
But, most likely, it was the Fire Prince's heart, which decided to overlook the laws of nature and make him long for this contradictory princess.
After talking his way out of his lamp, Flame Prince was wandering through the forest, trying not to burn anything. Of course he would not have been able to burn anything anyway, not while deep in thought.
"Why do I feel like this?" he wondered, "Why would Grod allow me to think this way of an opposite force?"
Flame Prince looked up at the sky.
Then he heard what sounded like humming.
Looking up ahead, Flame Prince found, by strange coincidence, Water Princess sitting at the edge of a lake.
One againg he looked up at the sky.
"What is going on up there?" the Fire Prince muttered.
He looked at Water Princess again, she was talking to a little group of fish.
"All right little fish," Water Princess instructed lightly, "start jumping."
The small fish started jumping around in the water.
"Jump, jump, jump, jump, jump, jump, jump." Water Princess giggled.
Water Princess clapped her hands as the fish stopped jumping.
"Yes, yes," she said happily, "good fish."
Water Princess leaned down and kissed one of the fish on its head, much to the fish's delight.
Flame Prince stood watching.
"So innocent, so different," he said, referring to the princess, "so why am I here?"
"She is a pretty princess." a voice in his head said, but it did not sound lke his.
"P-pretty...princess?" Flame Prince mumbled, staggering forward.
Water Princess continued watching the fish frolic in the pond, then she stood up.
It was then she finally noticed the fire elemental that had been watching her.
"Oh!" she gasped suddenly.
Flame Prince flinched.
"Sorry Princess," he said meekly, "I didn't mean to disturb you..."
"Gorgeous." Water Princess uttered.
"Huh? What?" the Fire Prince responded.
Water Princess got a closer look.
She reached her hand out.
"Wait you don't wanna..." Flame Prince said tensely.
Water Princess ran her hand through his blazing hair, creating steam on contact.
"Doesn't it hurt you?" Flame Prince asked.
"No," Water Princess answered, "I don't burn, at least not that quickly, but prolonged exposure could cause my body to dry out and evaporate, unless I have a source of water nearby."
"I can see you're not made out of water," Flame Prince replied, "but how do your powers work?"
"Like this." Water Princess said.
She turned to face the lack.
"Water powers GOOOO!" the water princess yelled.
With that, torrents of water projected from her eyes and into the lake.
When she was finished, she shook her head like a dog, then smiled placidly.
"That was...that was pretty cool." Flame Prince said.
I did not see this pairing used yet, at least not here.