What's the proper "connection" in this situation?

So there is a recent full-length movie about a young boy who falls love with another boy. There is a lot of bicycle riding and one of the boy's father is a self-centered popular singer. It ends when the two boys are at the father's concert and kiss in the audience, coming out to the father. Come to find out the same writer-director had a short film 13 years ago that also involved two boys riding bicycles and ended with them coming out to a self-centered singing father by kissing in front of him in the audience. The characters from the two films do not have the same names. I offered a connection to the recent film that it was a "spin off from" the short film with "same storyline" as the reason. Also explained more in the notes, but it was rejected. What would be the proper way to characterize the "connection," if "spin off from' was wrong?