Neither is cloning a "late twin."
With twins, the entire early cell structure splits completely in half, and it is a natural process. However, the twinning process does call into question whether clones might have a soul (mitigating in favor of this view.)
Cloning involves taking a complete set of living DNA code from the cell of an adult and placing it within the mechanisms of an unfertilized egg, after the 1/2 DNA code of the unfertilized egg has been removed.
This complete set of living DNA code, under the influence of hormonal and chemical baths, then takes over the cellular mechanism of the host egg and replicates in a fashion similar to that of a fertilized egg.
However, it is simply a cell line continuation of the donor's cell's DNA, in this case replicating in a viable egg.
At no point did this life begin.
I'd like to hear from a moral theologian on this. I'm probably wrong, but I do not believe such cloning is even possible, I do not believe it has indeed happened, and if it does, I still doubt it will have a new human soul.
God is not our little genie that we manipulate and call forth from his genie bottle at our whim and pleasure.
But why would both the twins have souls in the first place? Or does each twin get 1/2 a soul, since they split off from the original (soul-equipped) fertilized egg? Not to mention triplets, quads, quints, sexts, septs... You yourself said that the soulless clone would probably get a soul implanted by (apparently) Satan. Why don't you think this happens with identical twins, etc.?
(Come to think of it, my niece Julie does give my sister a lot more trouble than does her twin, Diana... :-)
So is the creation of the soul a physical process resulting from the combination of egg and sperm? Otherwise you'd have to say that everytime in-vitro fertilization is perfomed God creates a new soul to put into the new zygote.