OMG this, yes this! Yes yes yes I love this fetish! (Kind of like Smith's thing in the Matrix right?)
It seems like such a hot idea, I'ma try to find some work based on it.
Ok ummm on hand only one I remember is this cool Evangelion fic where
Ritsuko makes Shinji a clone of herself, and another one
with him becoming an Asuka-clone as well. Not quite through physical contact like described through.
There's an artpiece where Shinji/Asuka become identical Rei twins but I cannot find it now.