In families of multigenerational mixed ancestry, do you guess based on the whitest or least white?

[Sikeliot]

For instance, if you have a family of Dominicans, and one sibling looks almost passable as white, but another looks like a mulatto...

are you best off guessing that the siblings are both mulattoes and one of them happens to just look whiter, or guess that they have far more European ancestry and the blacker looking one has the throwback genes?

[Longbowman]

Buy them both a 23andme test.

IRL this stuff doesn't matter but if I saw a white-looking guy with a black-looking full blood sibling I'd know he was mulatto genetically, but still white in phenotype.

[SupaThug]

On the whitest,throwback genes are way stronger than people think.

[Sikeliot]

On the whitest

I tend to think so, yes. But I wanted to check.

For instance I have two young cousins I gave the photos of here; http://www.theapricity.com/forum/showthread.php?171166

If you went by the daughter's phenotype as opposed to the son's, you'd overestimate their African, and you know by looking at both parents... the mother is white, and the father passes as fully European.