>>102314193He wouldn’t be close to Gwen because they never had their summer road trip together with Max. And Kai would be right out of the question, because she only met him through their respective grandfathers being old Plumber buddies.
Julie is a bit of an odd duck though, because they met through school as opposed to Omnitrix shenanigans. He MIGHT get with her the same way he did in Alien Force, by seeing her around and finding her cute.
Or, if we want to go more in character for Ben 23, perhaps Jennifer Nocturne is more his speed - beautiful and famous, like him.
I also wouldn’t /totally/ discount an Alien waifu for Ben 23. He eventually learns that not all aliens are evil. Maybe he’ll fall for one when he gets older, and more accepting of other species. Looma and Attea are probably too “exotic” for him, but maybe a half breed like Ester wouldn’t be.