I haven't been asked that here yet, but I figure I'll answer it anyway just for shits and giggles. The answer is that at one point, Gelphox and an unnamed Serperior-phox who would go on to become Kasi and Akesi, were simply alternate forms for Professor Alopex, who also didn't have a name yet. Then divergent evolution took place, and Alopex, Gelphox, Kasi and Akesi all became separate characters. (And also Cirrus, but they came later, a little bit after Gelphox became a separate character but before K&A did.) Then I had the idea for a thing where I would create a half-Delphox OC for every single type. The other halves of each one were going to be as follows:

⚪Normal - Smeargle
🔥Fire - Fennekin/Braixen (Alopex)
💧Water - Primarina
🍃Grass - Serperior (Kasi and Akesi)
⚡Electric - Ampharos
👁️Psychic - Alolan Raichu
❄️Ice - Chien-Pao
🌑Dark - Pangoro
🐉Dragon - Goodra (Gelphox)
💖Fairy - Dachsbun
👻Ghost - Hisuian Zorua (Cirrus)
🐞Bug - Scolipede
⚙️Steel - Gholdengo
💎Rock - Midnight Lycanroc
👊Fighting - Lucario
🪽Flying - Drifblim, probably
☠️Poison - Salazzle
🏔️Ground - Nidoqueen

Maybe someday I'll make the other 14. I've been thinking about fleshing out the half-Lycanroc one a bit more recently.