They are obligate parasitoids with a noted sexual dimorphism. The males are more visible and look like flies, but the front pair of wings is turned into twisted stick-like things (instead of the back pair, in true flies). As a larva, the male finds a host, and pupates. After he emerges, he lives only a few hours as an adult, and bites his way out of the host to look for a female. The female larva finds a host and then never leaves; it sticks its sexual organs outside the host for the male and then withdraws them; the eggs hatch inside the female and eventually leave through the breeding canal.
(Grossed out, yet? Nature can be a horror writer.)
So here's how it might apply to superheroes. I of course think it's more interesting if this applies to all (or most) superhumans, but you're free to have it apply only to some or just to have it as a crazy theory that someone expounds.
Let's posit a parasite that can control its host, as it seems very likely that a number of them do (see discussions of the fact that some Strepsiptera can cause their host to linger on the tips of plant leaves, or of Toxoplasmosis gondii, for example). We'll also say, for the sake of argument, that humans can develop superpowers, because without that, this ain't going anyplace. It's up to you whether that's something in the parasite genome that it gives to its host, or whether it's something in the human genome that's activated by the parasite.
My taxonomic biology is rusty enough that I don't remember if we need to create a new class or order for it; let's just call it Paraplasmosis kalelii.
So my thesis here is that all superhumans are infected with P. kalelii. Superheroes have one sex, supervillains have the other. (Because the sexually active adults are sessile, there's not a lot of difference; I'm not totally sure that you can say "superheroes are one sex, supervillains are the other." There are clear cases of overlap. P. kalelii might in fact be a fungus (there are some compelling cases) that permeates the body, and a team of heroes or villains might just be a colony. I digress.
There are some similarities between the sexes, and just being near another sexually active P. kalelii can force sexual maturity. (In this case, "sexual maturity" results in getting powers. I suspect that there is a subspecies that creates physical perfection and subtly enhances healing; the Bat-family has this kind.) So being near a hero or villain, you can get powers if you're already infected. A stressful event might be enough. There might even be a weird set of gene transfer rules, so that Peter Parker wasn't going to be a spider-man, but the spider bite counted as a traumatic event and there were spider genes in the bite; the P. kalelii in his system used those.
When an infected pair of hosts fight, chemicals are transmitted between the male and the female. In the early encounters, they trade a number of chemicals that can lead to one becoming sensitized to the other: an arch-foe is like a lover in that sense. The chemicals are compatible. In some cases, the two never hit it off, chemically....you have one-off villains who then seek out other heroes, looking for someone appropriate.
The whole business of capturing and holding the hero is programmed: that's when the actual sperm transfer takes place, (in some way that isn't X-rated, you filthy-minded reader). The sperm looks innocuous: it's more like pollen than sperm--you might mistake it for dandruff or dust. All it needs to do is find its way to the mucous membranes, such as the sclera of the eye or inside the lungs or in the mouth. From there, it finds its way to the female.
Eventually the female lays eggs, which are passed out of the host body, probably as sweat, though it might be as exhaled particulates. Like many parasites, there's a complex life cycle, but at the right stage it needs to find a genetically-compatible host.
From a game point of view, that can be anyone; very few of us control what we exhale or excrete to the extent that someone infected can avoid
Now, how can you use this in your game? Well, assuming it's true for some or all of the supers in your world, then there might actually be a biochemical cure for being a super. A rigorous treatment of antibiotics and a regular screening, and you might not be a super any more. (Depending on what happened when the organism activated those genes, you might not have a choice to be a super. It can go both ways.)
It also means that the super-soldier program gets much, much simpler: they infect suitable hosts. The though part is trying to control what powers they get.