Quadratic twins.

If two identical twins both had babies with another set of identical twins, their kids would technically be siblings.

If two identical twins both had babies with another set of identical twins, their kids would technically be siblings.

I feel like this is wrong but I don't actually know how to explain why.

their kid would look like if you were standing sideways next to a mirror to reflect one half of your body to make a symmetrical person, except you stand too close so your eyes and nose are too close together and pinched, and the body warped

so like an inbred mirror reflection I think

Technically they aren't identical. One has a penis, the other a vagina.

But, semantics aside, recessive genes would prevent sexual cloning 

They would combine to form a 4-dimensional human existing outside of space-time, where they would multiply exponentially and lead humanity into the next step of evolution.

The Übermensch