Jamie H. Cowan
From Jenny Everywhere Wiki
Jamie H. Cowan (full name as Jamie Hamilton Cowan[1]or Jamie Hebert Cowan[2]; born in Druimblaire[1], Scotland[2] in a far-off year[1] or 1764[2]) wrote the short story Letter that you should all read for Jenny Everywhere Day in 2023. Within the story, he introduced the concept of Jenny Not-Here.
Additionally, Cowan has also written Everywhere The First - the first part of the serialised Where In Every World Is Forever: A Jenny Everywhere Tale series.