AU. Academy Fic. Jim's maternal bloodline is that of Federation alligned Humanoid race known as Veenans (Veena for singular), a peaceful, advanced race that are also heavily empathic. Because of their genetic evolution, some are even telekenetic. This species is uniguely united; seeing as all others as "brothers" and "sisters". Also, because of their genetic makeup, Veenans hardly, if ever, engage in sex with someone without a proper empathic bond to keep them stable.  One sign of a Veena is that their irises glow slightly when they are emotionally overwhelmed or excited. Veenu blood is strong in Jim, and after joining Starfleet, becomes infatuated with the Vulcan professor Spock. Due to Spock's half-Human heritage with a blend of Vulcan passions (albeit repressed), it appeals to Jim, who begins making an empathic bond with the Vulcan unknowingly. Spock finds Jim's company- as well as that of Uhura's -appealing. He, intially, sees Jim as nothing more than a friendly aqcuaintance, but overtime the Cadet's intelligence and friendly personality attracts him more and more. Eventual K/S. POINTS: Once Jim finds out he is unconsciously bonding with Spock, becomes horrified that Spock may not reciprocate, and tries to avoid the Vulcan in order to find a way to dissolve the bond. Spock becomes suspicious and won't take the hint to leave Jim alone. BONUS POINTS: Jim's mom is a sweetheart, and Jim confides in her his feelings with Spock, who then helps Jim come to accept what he feels. (Due to Winona being Veena, she is affectionate and close with her son, despite losing her husband at his birth.) BONUS POINTS: Before Spock realizes he's in love with Jim, Jim becomes slightly protective/possessive of Spock. Not violent- just somewhat defensive and territorial. Jim cannot help the primative instincts rising within him, and a few times confuses his friends, himself and Spock by the protective streak that he has over the Professor. PURE LOVE: If Spock's parents come for a Starfleet gala, and bring T'Pring and her family to visit as well. Jim does NOT like it, and gets paranoid/territorial of seeing T'Pring and Spock together.

So..Kinda' a long prompt but I want a fic where Jim is only half human. The other half of him is some type of animal/alien creature. This could be from illegal genetc re-engineering, alien technology (like the fiasco with Janice Lester), etc. But they are unable to fully reverse it, maybe it occured when he was a child away from Earth for the first time(Tarsus IV)? Anyway...Jim goes into heat and Spock as one of the few non-humans onboard is effected by the pheromones Jim is producing. Spock chases him all over the ship before eventually catching and breeding him. Eventually they both get their rational minds back and want to ignore the whole embarissing episode, but find that difficult to do when Jim starts having some very strong "nesting" behaviors. Maybe he starts building a nest with stolen clothing, blankets, etc. in a jeffries tube.

Alien!Creature!Jim
Mating Heat
MPreg
Bonding
Nesting Behavior
K/S