There are sons and daughters who don’t look like their parents at all. We call them “Onikko 鬼っ子” in Japanese, which literally means the child born or brought by an ogre, not by his / her biological parents.
Onikko doesn't necessarily mean derogatory. For instance, when we have a brilliant child brought up by mediocre parents, we describe the child 鳶が鷹を産んだ子 – tobi ga taka wo unda ko – a hawk born by a kite. The hawk (child) can be a kind of Onikko.
What is the expression in English for the son or daughter who doesn't resemble his / her parent in face, figure and temper though they are their parents' real child?
Best Answer
Usually it would be polite not to mention the fact that a child doesn't seem to resemble its parents, since this might imply infidelity on the part of the mother (not good for Susan George in the 1975 film Mandingo). But you will sometimes encounter OED's sense 6a for...
This noun usage derives from the (now rare) verb sense...
As @ronan comments, facetious "He looks like the postman / milkman / etc." is not uncommon.
There's also throwback (reversion to an earlier ancestral type or character; an example of this). But unless accompanied by a reference to a specific grandparent (or perhaps great grandparent) that the child does resemble, this invariably has negative associations (with the implicit unspecified ancestor being a Neanderthal or some other precursor to homo sapiens).