It's with much excitement that we can now verify the Devilgotchi Twins with photo evidence!
This character is called "Twin Deviltchi" (ふたごデビル Futagodebiru) according to the wonderful Tama Wiki.
They were obtained by keeping Girl Deviltchi alive with full Friendship (4) and Devil Points (DP) between 80 - 95. At the time she evolved into the Twins she had been in my care for 6 days and 1 hour. Her DP were at 90 at this time.
We'd like to thank everyone in the #Spooky-Hatch channel of the Tama Discord for helping out!