> “would seem like common sense, but never had been shown,”

and might not be the case "in general"

I mean convergent evolution lead to different species with very different DNA looking similar.

And evolution doesn't choose what to do, stuff (mutations etc.) "just happen randomly" and some things propagate more then others.

So for me two unrelated people with rather different DNA happen to look extremely similar seems to be quite reasonable.

Through some unrelated people having rather similar DNA is as reasonable.