This is more a hypothesis than a question, but I thought I'd throw it out to E-hellions to see if anybody has thoughts on this.
In my (admittedly small) extended family, most people don't have more than two kids (just the way it worked out). And I've noticed that it seems like one kid takes more strongly after one parent, and the other takes more strongly after the other parent.
For example, while I share many traits with my mom, I am without doubt my father's daughter. I inherited his body shape, his good-at-books-and-schooling brain and his sense of humor. My brother, who also has the sense of humor, inherited my mom's body shape and her good-at-hands-on intelligence.
Is this true in your family, or am I just seeing something that isn't there?
I think it can happen that a child has the general looks and personality of one parent. But it can also be total random.
My brother Ted has two sons. One looks exactly like Ted and has quite a bit of Ted's personality. One looks exactly like Ted's ex-wife, but is nothing like her in temperament, and only partly like my brother.
My brother Ned has three kids. All look more like my SIL than Ned. But the youngest has Ned's personality, through and through.
My brother Fred has a kid who is eerily identical to my brother Ted in looks, but not in personality.
I'm one of seven kids. Six of us look just like Dad, but two of us got Mom's eye color. Personality-wise, we are all over the place. The seventh sibling--we had no idea who he looked like. In fact, some people, just seeing a family picture, would think that he was adopted. Then someone found a picture of Dad's father in his 20s and everyone agrees that Sibling looks exactly like a young Grandpa.
I think some of it is just that with two parents and two kids, there's a natural inclination to match each kid to one parent.
And genetics is weird. I have two red-headed grandparents, two brown-haired parents, one red-headed sibling. That sibling has one red-headed child, and one brown. One of my brown-haired siblings married a red-head. Their 4 kids are all red-heads. And yet, red hair is supposed to be recessive.