My family:
Mother - INFJ
Father - ENTP
Older brother - ENTP (even looks exactly like my father minus 25 years)
Older sister - XXXX (Bipolar Disorder, so i'm not even gonna
try. Sometimes some sort of ISFP, sometimes some sort of ENTJ). She's very nice and all, but extreme.
Me - INTJ
Younger sister - INTJ
Both of my parents value emotion and logic, not just either, and that's how they taught the rest of us.
I'd say that they're both close to the T/F divide. And that's how most of us turned out as well.
For instance, Fe isn't supposed to be one of my strong points, but it is in fact just as strong as my Te function in terms of how well-developed it is.
That says nothing about my preference to use it instead of Te, though.
I do believe that some traits are inherited. Most of us kids share a strange neurological thing called synesthesia.
My father and my big sister are the only ones who don't have it.
Mother, my older brother, me and my little sister all associate numbers, feelings, words, people and sound with colors.
I know that the brain isn't some ethereal heavenly thing that just occurs.
It's made out of flesh and blood, sort of a biological computer.
If you combine your parents inherent traits, you get a result.
I do believe that these results can be swayed to some degree with nurturing, but the apple usually falls within a few meters of the tree when it comes to personality.
For instance, I hardly ever met my paternal grandfather. Yet I look like him, sound like him, say things that he did, do gestures that he used etc.
We even share a couple of hobbies.
I have two memories of the guy. One where he serves me some strawberry ice cream and one from grandma's funeral, where he cried and I remember feeling sorry for him.
Grandpa was an INTJ as well.
I don't remember grandma much at all and dad doesn't talk much about her.
I do think my maternal grandfather was something like an INTJ as well. He and my older brother were and are, respectively, my closest family relationships in a way.
He was a bit harder to type, though. He was very introverted in that Zen way, almost.
Very kind and knowledgeable, but not very outwards with it all.
My maternal grandmother is some sort of hyperactive ExFJ.
Definite Fe-dominant, though.
My uncle (mother's brother) is a definite INTP
nerd. He designed a working engine at 15 and he wrote the system that controls most swedish hydro power dams when he was about 30 (I think), among other things.
His wife is an ESFJ, and my cousins are INTP and ESFJ. Both guys. Boy, do they fight...
To a large extent, I think it's genetical. This is just personal stuff, but I see it everywhere.
If we inherited diseases, pigments, voice, behaviors from dead relatives...
Isn't it then possible that we also inherit the basics on what makes us what we are?