Previous parts in this Theme-Conflict Integration Series are Indexed at:
One of the oldest story driving conflicts is termed, "Man against himself." But of course, today, we read that as "Person against self," stripping it of sexual innuendo.
Women can oppose their own interests subconsciously, as well as men (maybe better!)
And of course non-humans might very likely be the same.
The most interesting non-humans would, of course, lack the ability to be their own worst enemy -- in many ways, Spock was originally depicted as such an alien.
So to depict a Romance between a human who can thwart their own interests and a non-human who lacks that trait (and thus doesn't really understand it), one must first examine the issue of "Internal Conflict" and how such a conflict is resolved to reader satisfaction.
Once the writer has a clean, easily expressed theory of how humans oppose themselves internally (and why, and when), then it becomes easy to design the Alien Soul Mate for the human main character.
Concocting a Science Fiction theory of human psychology has at least two main parts:
A) Name the two parts inside humans that could possibly conflict?
B) Name the part that wins.
We have extant theories of Conscious/Subconscious, Yin/Yang, and Body/Soul.
Maybe all of them operate simultaneously -- or maybe none of them are true, just useful approximations.
Choose which maybe you want to use for your Worldbuilding.
Yes, these 3 choices for the 2 parts of humans that cause inexplicable behavior (like falling in love, for example), define 3 separate and different "worlds" you can build. They are elements of world building, and each defines a sort of "magic" that can (or can't) work in that world.
Humans have been striving to define "what it is" inside us that gives us such trouble, as individuals and whole societies, for thousands of years.
So choose (or invent) a dichotomy to insert into the axioms defining the world you will tell your story within, and then choose the Rules of Engagement -- how they fight, why, and to what end.
The most obvious and natural one for a Science Fiction Romance world is Body/Soul.
Romance is about the sweeping force that dissolves the personality's bonds to "reality" -- to the practical, the everyday, to responsibility (Saturn) and accountability (Mercury ruling Virgo).
People swept off their feet falling "in love" behave unrealistically (Romeo and Juliet), immaturely, or as if they are ignorant of the strictures of reality (an office affair between a Boss and a Janitor, when both are married-with-children).
Romance (Neptune) dissolves common sense, and makes everything and anything possible. The mental "executive function" becomes paralyzed. There's nothing inside, no self-discipline, that will stop you, and no awareness of how you will feel about or deal with the consequences.
You do what you want and to hell with the consequences.
That is a favorite excuse in Romance novels for having sex with an inappropriate (or forbidden) individual.
So when Neptune transits hit full force, igniting ferocious sexual urges between a couple, Neptune wins. There is no internal conflict because the Executive Function of the personality is not functioning.
NO CONFLICT = NO STORY
Thus the "irresistible hunk" story is not actually a story at all. If the hunk truly is irresistible, there is nothing to oppose his advances, nothing there saying "no!"
Or vice-versa, a guy can run across a woman he can't resist.
But if he can't resist, there is no story to tell.
Story (and plot) are all about RESOLVING CONFLICT, so if there is no conflict there is no resolution, thus no satisfaction in reading about it.
So in a universe where humans are constructed with an internal dichotomy best expressed as Body/Soul, it is the physical (pheromones, physical arousal) of the Body that can (and often does) conflict with the spiritual fulfillment the Soul seeks.
You can use the "model" of Body vs. Soul to create Soul Mates whose bodies won't cooperate.
Romeo and Juliet is again a good analogy, as they were spiritually attracted Soul Mates born on opposite sides of a feud. Hatfields and McCoys. Israeli and Palestinian.
Throughout history there have been many political conflicts conquered by Romance. Kings married their daughters to sons of the main enemies to settle disputes, and history records how many generations hence that settlement lasted. Very few historical texts detail how the daughter-and-son actually felt about it. Those novels are being written now.
The body can be born a non-human on some other planet (or space station) arriving at Earth's solar system carrying a Soul which is the Mate to a Soul born human on Earth.
Such a "love" has to conquer all the seething dynamics of First Contact, or worse, the ending of a long interstellar war.
Now we come to the Influence part. If you choose Body/Soul as your world building dichotomy, then you must decide (sometimes by writing the whole book first) which "wins." Or more broadly put, how the conflict resolves.
What are the options for resolving a conflict between civilizations?
Well, we have a pattern laid down for us thousands of years ago, which has repeated a few times, and may actually turn up again as we make a First Contact with non-humans.
The story is told in the Bible, and by Hollywood (Cecil B. DeMille), as THE EXODUS.
And the style of the conflict resolution writers can rip from this classic, is Persuasion.
As humans, pure physical bodies, basic primate species, we behave toward each other in a "dominance" pattern, always conquering, opposing, WINNING. It's in video games, sports, politics, war. You just have to win. It starts in infancy with screaming until large hands bring relief.
Toddlers learn to insist until they get their way. Toddlers learn that Might Makes Right because parents will oppose their insistence with forces the Toddler can't match (pick him up and just put him in the car seat.)
Sometimes, parents have the leisure to distract the toddler or just let the screaming exhaust him. But the parent always wins.
Later, the parent may try persuasion, but by then the twig is bent and the tree growing robustly.
Basically, primates survive toddlerhood by having their Will overridden. Toddlers who win the battle run out in the street and get run over by a car. It happens. All our toddlers would do that, given the chance. Having that Will thwarted by Adults grabbing him up just teaches Might Makes Right.
After Toddlerhood, other lessons split our population into those who bend under force, and those who fight to the death.
Any given individual may choose (free will) either strategy, any combination, or invent a new one to try.
But in the end, how we influence each other comes down to a dominance exercise. How do we get each other to behave properly?
Today's readership is swamped with discussions about violence and the use of violence. The language of violence is used in News Headlines to describe mere words said to or about someone. "...Ripped Into..." "...blasted..."
This is all about one human forcing another to change an opinion or course of action.
In The Exodus story, we see 10 "plagues" (natural disasters, we'd call it today). The conflict that makes this a "story" is between the Creator of the Universe and Pharaoh. They vie for possession of a "people" -- the Jews.
Having granted humans "free will," the Creator first demonstrated the reason Pharaoh should release the Jews as that He was better at controlling Nature than Pharaoh's Magicians. That went on for 5 plagues and Pharaoh tended to give in, but didn't change his opinion. Then the Creator argued for 5 more plagues to persuade Pharaoh to change his own mind. The Sages point out that we can learn from Pharaoh's eventual agreement that Persuasion works better than logical equations about brute force.
Of course, we also learn that Pharaoh sent chariots after the fleeing mixed multitude (which included a lot of Egyptians throwing in their lot with the winner.) Their fate is depicted by Cecil B. DeMille even though Cecil got the "parting" of the sea wrong.
Nevertheless, original sources notwithstanding, all of your readers will probably visualize the Hollywood version of the parting of the sea and wipe-out of the chariots. The general public has been persuaded. The general public is under the influence of visual artists whose tools are limited.
The general public, your reader, does not fight that influence.
So, how does one Character exercise Influence over another in such a way that the influencer "wins?"
Which prevails, Body or Soul?
The human primate Body uses Force -- force of muscle, force of size, force of authority bestowed by Kings or Presidents, force of pheromones, force of intellect (strategy, tactics, blackmail), force of Power (I'll make you a star, or ruin your career).
The Body argues by making it abundantly clear that it is to your advantage to do something against your better interests. Go along to get along. Bend (as Pharaoh did) then snap back when attention is elsewhere. Agree to anything under duress, defy later.
The Soul argues right and wrong, ethics, morals, living a Code of Conduct which is to the advantage of the Soul even when it costs the Body dearly. The Soul adopts Causes, Crusades, Movements, Idealism, Aspirations. But the Soul habitually Loves -- loves all humans, loves all Bodies, even when they are staunchly opposed to the Soul's purposes.
In Romance genre, including Science Fiction Romance, Love Conquers All is the basic theme, the tenet of all the worlds that belong to the genre.
Soul Mates always gravitate toward each other, like two magnets, snap! Bodies have to accept that, even when it thwarts the body's purpose. Souls win, if not in this life, then in the next incarnation.
Bodies, brains, minds woven of the stuff of this concrete reality often embrace "being influenced" -- which essentially means adopting the Group's prevailing opinion, agreeing with opinions shouted forcefully in public, accepting the opinion of "authority" or "experts" who know better than you do.
Souls, aware of being eternal, do not need to "fit in" to survive. Souls strive and struggle to get their Bodies to live up to ideals, like a horse trainer "breaking" a horse -- or perhaps the wiser ones use less force and more persuasion, luring the physical body with physical pleasure as reward.
Souls resist Influence; Bodies seek it.
Humans have both a Soul and a Body welded inextricably to the physical world. Any human will sometimes fight being Influenced, and other times adopt the Influencer's ideas as their own. In other words, humans flip-flop between body and soul dominant. Any given human might flip-flop on you at any given time -- and not be able to explain why they changed.
If you start a story in Chapter 1 with a Character succumbing to the Influence of another Character, the end of the last Chapter, the very last page, depicts the first Character throwing off that influence.
That is the innate structure of "story" -- short, medium or long -- the beginning is where the two forces that will conflict to generate the plot (to generate the deeds, motives, and Events) first come into contact.
Thus choosing your opening scene as the point at which one Character willingly adopts the opinion of another, you telegraph to the reader that Influence is the conflict.
The Theme is what readers read for, whether they know it or not. The feeling of satisfaction at The End is powered by dawning comprehension of the Theme.
The master theme of Romance is Love Conquers All. But it has many sub-themes - and in fact, almost any theme can be subordinated to Love Conquers All and still remain congruent to everyday reality. I've never found a theme that can't fit Love Conquers All.
If the story opens with a Character Influenced by (an equal, a superior, Good, Evil), the story is about the gyrations necessary to fight off that Influence.
Once free, the Character may choose to adopt that same opinion, and might even become an Influencer disseminating that opinion.
But the story ends where the Character is free of Influence.
THEME: Humans must be free to choose.
THEME: Humans always choose wrong.
THEME: Humans can't be trusted to behave well.
THEME: Alien Values Are Better For Humans Than Ancient Human Values!
THEME: Non-humans are incompatible with humans.
THEME: Certain non-humans aren't so bad.
THEME: It's all right to be human.
THEME: It is not all right to be human.
Keep going to find your best theme that reveals the natural laws of your world and how those laws conflict or contradict each other, creating Characters who fight to exist in your world.
If the inner conflict is Body vs Soul, then the Themes can be fabricated from adages such as the proverbial, "If there are two wolves fighting inside you, which one wins?" "The one you feed the most."
So if you feed your Soul the most, practicing idealistic decision-making, then your Soul will dominate your body. If you feed your body the most, indulging carnal appetites, then your body will dominate your soul. Is that true in your fictional world? Do your Characters have a choice which to feed the most?
In other words,
THEME: Humans are creatures of habit.
THEME: Humans rebel against habit, periodically. (Uranus transit; mid-life crisis)
THEME: Humans prize freedom from the influence of other humans.
THEME: Humans prize the influence of other humans who (fill in the characteristic, sweet, kind, beautiful, rich, powerful...).
Always remember your THEME is what the main characters' thinking finally evolves into, not what they start out thinking when the conflict is joined, or before the conflict is resolved.