My response: The two are linked.
Parental inheritance - mostly, but not entirely, from genetics - of factors such as intelligence, personality, some special abilities, plus physical attributes and diseases - is very important; and there are also ways in which 'spirit' - i.e. divine plan - is significant. However, these spiritual factors we either do not know, or cannot usually access (although personal revelation is a possibility).
This non-hereditary influence is most obvious when a child - perhaps one among siblings - is very different from his parents; but the situation applies to everyone to some extent, because each human is distinct.
I mean that the identity of our parents is influenced by things like our pre-mortal relationships as spirits, and the fact that we were divinely 'placed' with certain parents - in certain general situations of time and place - for our own good.
By 'our own good' I do not mean our health and happiness during mortal life; but in terms of the secondary purpose of mortal life. The primary purpose is to incarnate and die: everybody achieves that purpose. The secondary purpose is the hope of what we may accomplish, spiritually, during life - what we most need in order to progress towards divinity.
So, common observation - backed up by research - tells us that heredity accounts for much of human differences, but our parents were chosen for us, they are not random - so the spiritual aspect is primary.
This dual influence is vital in binding the universe. We are first sons and daughters of God, and that relationship is literal and makes everyone part of one divine family; then secondly we are sons and daughters of our parents, which is also a real and literal relationship, and gathers our spirits into multiple specific human families.
Then, thirdly, there may be a possibility of marriage, which incrementally links the various human families; and creates further combinations and possibilities.