Improving on the human male sex organs
Oh, he still has a penis and a scotum, of sorts, but they look and function a little differently than human males. I decided to give my human male a few surprises (pleasant ones, once he gets over the shock) and let my alien male have the improved version of the male sex organs. Don't get me wrong, I love the ones men have now, but if you can create the fantasy, why not go for it?
Since my hero is somewhat reptilian in nature, I've made his penis snake-like and functional. Kind of like having a python attached at his groin, one that can become slender and long for those hard to reach places, or thick and filling for those nifty prostate massages. It squirms and wiggles, massaging and teasing as it strokes in and out. It can also wrap around things, like the alien's partner's shaft, and undulate while his hands are busy elsewhere. See I said I'd make it better and pleasantly so!
Since the alien, Talos, is a 26th century bounty hunter from a warrior race that shuns much clothing, this precious organ retracts into the alien's abdomen for protection if necessary. His scrotum-like pouch is actually a nest of 4-5 inch long tenacles that adhere to the body of his sexual partner to prevent dislodgement. They too can rub and stroke the flesh they are near. In the alien's species it is for holding and penetrating the unfertilized placental sac the female gives birth to in a birthing pool. Intercourse isn't neceassary for them to procreate. It's for pleasure. Same gender marriages are a given in many warrior cultures (look at Alexander the Great)and his is no different.
Oh, and his new human love? That's a 18th century Earth pirate he kidnapped. (18th century English seamen were well known for a love of the three b's -- 'beer, 'bacca, and bum'!) Bloody lovely arrangement that. At least for my story!