Pleasure and "knowledge" allows two or more memes or memes generators to spawn new ones, as well as be educated themselves.
However, using magic one can duplicate anything while giving the duplicates new souls. E.g: Valentine Gellar, or Thomas Riker. The devils/orcs used it to fork entire universes.
Like the Unix “fork()” system call, wizards' souls in forked universes are aware that they are the "child process". However, vampires' souls didn't have that privilege!
There are mergers / joins too. Also note Microsoft Windows being merged into GNU, Linux, and WINE. Do note that the two-or-more original souls remain intact and may reappear in different contexts in the future.
One can spawn imaginary worlds which share similarities to our own. E.g:
The Beckyverse - Sarah Michelle Gellar (SMG) was not born, but Summer Glau, Emma Watson, and Shlomi Fish were.
Wizarding World (= Terrestrial spin on Harry Potter)
The Big Bang Theory show.