I have 3 siblings. We have some things alike, like the Cherokee slanted eyes of our grandmother.
Other than that, we are all extremely different. Brother is well over 6 feet tall. One sister is barely over five feet.
Two had straight hair, one of us has very curly hair, one had thick wavy hair. The hair colors vary, two born with brown that stayed brown. Two born blond that later turned brown in adulthood.
Our teeth are also very different. Two needed braces, two did not.
We have all long had children. The brother’s kids look like him and his wife. Even though he has sisters, his kids don’t look like his sisters.
My kids look nothing like my brother. My sisters daughters do not look like my brother.
So my own real life experience is telling me that Thomas Jefferson’s child by Sally Heming, who looked enough like him to be mistaken for him, was not fathered by a nephew of his.
The resemblance would not be very strong at all to Thomas Jefferson and his Carr nephews.
I supposedly have 1/16th American Indian ancestry myself, on my mother’s side, yet my mother and sister had blond hair and blue eyes. I have brown hair (partially gray now) and brown eyes.
It depends on which genes are passed down. Evonne Goolagong, the tennis player of decades ago, was supposedly Australian aborigine in race (must have been mixed), but she didn’t look much like an aborigine to me. http://media.gettyimages.com/photos/evonne-goolagong-of-australia-at-wimbledon-circa-july-1971-goolagong-picture-id462775778
Australian aborigines — http://i.dailymail.co.uk/i/pix/2015/01/28/0703198F000005DC-0-image-m-6_1422446578540.jpg
Yes, fathers and children often look alike (I don’t look like my parents, though, except in being very tall and skinny), but it’s a chance draw when genes are distributed to the next generation. For instance, brothers on average share half their genes. It’s by one half less likely — but quite possible — for a first cousin to look more like a person than one’s own child.
Then it’s by one half less likely again for the next generation (if I’m not mistaken in my calculations about genes). In any case we’re not talking about extremely remote chances, just something slightly less likely than what would be expected.
