Yknow, this is kinda why i like fish, and coyotes.
Zoo romance can go pretty deep.
Fish don't really form mate bonds on the basis of sexual pleasure, their bodies even make such impossible.
Yeah, i find them genuinely hot, and fantasy sex with a giant marlin in is fun, but, irl, it's their bonding that gets me.
One species, mahi-mahi, mate for life, and form bonds so close that, even when one is caught, their mate will refuse to leave the area, desperately hoping the being they've spent their lives with may yet come back. Fishermen, unfortunately, exploit this to double their catch.
Coyotes end up doing a similar thing. In more natural circumstances, without hunting pressure, coyotes turn to monogamy as populations stabilize. They pair up, for life. Mating occurs only once a year, but for the rest of the time, they're ride or die. They hunt together, explore together, and think together.
If one does eventually pass due to human actions, such as trapping, the other seems to mourn and even seek revenge. Coyotes who lost mates due to traps make a point of finding traps wherever they can, figuring out ways to disable them, and then they defecate. Right on the trap they disabled.
As for forming relationships with humans, things get a bit tricky when it comes to finding examples.
With fish, examples are vanishingly rare, due to humanity's general attitude towards fish. We see them as dumb things, barely worthy of being called animals. We deny their ability to even feel pain or emotion, and as a result, a relationship with them... is almost never tried. There are cases of divers forming a relationship with a fish, having them come back again and again, but these stories a bit harder to decipher.
I will make a whole post about it someday.
Coyotes...
Well there is one example i know of. Coyote monogamy is triggered by specific circumstances. Some complicated combo of lack of pressure, territory claims, and nearby packs... No matter the cause, we don't see it much in captivity, but one formerly famous coyote, Dakota, seems to have formed such bond with his rehabber.
Unfortunately, there isn't much to go off. Due to, shockingly credible, death threats, Dakota is kept hidden on some other part of their sanctuary, and can't even really be mentioned anymore.
But from what his caretakers could tell us back in the day, is that he has formed a shockingly tight bond with his rehabber. No one else can approach his case without much complaint, and he only ever comes to trust other females, IE, ones he knows wouldn't take his mate.
It ain't much, but it does seem like a classic coyote pair bond, only with a human. A relationship built partially off attraction.
I agree that with some animals, such as dogs, their desire may be related only to assisted masturbation, just sexual pleasure... But there are many species out there that transcend this and can form these mate bond with, attraction to, humans.