Is that “as from the same litter”?
We may never know, since @Lissa hasn’t been seen on the board in 15 years.
Probably just lurking anonomously. Dopers never really leave.
I guess think of specific genetics as being like those “identi-kit” things for police to construct a picture of a suspect. Certain genetics determines chin shape, cheekbones, jaw squareness, cheek pudge, eyebrow ridge, etc. This would explain why siblings have a family resemblance, but everyone inherits two of everything, one may be dominant or both may mix to produce face characteristics. If you happen to end up with the same or similar collection of these genes as your doppelganger, your face will look very similar. Of course, accidentally having the same genes for face does not guarantee anything else is similar, from personality to IQ components to height or predisposition to obesity…
But…those genetic similarities are related to appearance.
And the habits and inclinations that they share also contribute to appearance (obesity, etc.).