Hi Hops,
Possible, yes, but genetics are, by far, the greatest determinant of personality characteristics—explaining, in general, 50% of the variance. Now, if one grows up in an environment that is radically different than the norm, e.g. losing a parent one is attached to at a very early age, personality can be dramatically affected. But absent such trauma, I always, in my “work,” look first at genetics. I have come across many examples of families where one sibling has great empathy, while another has little or none. Yet, they both grew up in the same household with the same parents. The likely explanation: One child got a particular set of genes, while the other got a different set (of course the two children got many of the same genes as well).
If you want to read about some of the wonderful work done in this area, take a look at Nancy Segal’s book about the Minnesota Twin Study:
Born Together—Reared Apart. Here you’ll see the data on such variables as IQ, psychopathology, religiosity, conservatism, authoritarianism, and many others.
For many, many reasons, some of which I’ve talked about on this Board, my life has been a lesson in genetics. When I began my career, I never would have guessed this would be so—everyone I knew talked about nurture, not nature. Everyone except Steven Pinker—his book,
How the Mind Works, was my introduction to another way of thinking about psychology and therapy. (That’s not the only reason I’m indebted to Steve: 35 years ago he and his wife at the time, Nancy, helped my wife and I move into our house. For that I will always be grateful

.)
Richard