since you cannot creat an exact clone, especially in terms of memory (no such thing as the sixth day), id find it very suspicious...

but, in the hypothetical... how would you know which is which? and, if there is no way of telling, why NOT work out a threesome? seriously... if you cant tell and they wont compromise... the only thing you can do is walk away from both since it would be an emotional crime to walk away from one and stay with the other.