SUPPOSEDLY, types are determined by brain function development more than anything else, but I think the type itself is often the result of the parents’ types as well as your growing up environment. I don’t think your experiences growing up can literally change your personality type, but I do think that what your parents value and instill in you can alter your natural behavior — both in positive and negative ways.
For example, something you hear about my type (ENFP) all the time is how we are chronically late everywhere. That was a major stumbling block for me in determining my own type, because I am never late. I’m very time-conscious so I always leave early, get there early, and am frustrated if other people are late. It wasn’t until later that I realized my parents’ emphasis on politeness as being on time made an impression on me, so they trained me to be on time, not only for its own sake but out of respect for other people. They developed that Te aspect of my personality early.
I know an ISFJ, on the other hand, who is often late, which isn’t usual for an ISFJ; but she was raised in a free-spirited family who spent much of her childhood in traveling fairs, fostering a bit of a wanderer-like lifestyle. As a result, even though she displays clear Si-Fe traits, she has a bit of a restless, wandering spirit who would probably drop everything and go traveling at a moment’s notice if given the chance, because her Si remembers how much fun it was to travel and see new places.
I think our functions develop according to how much our environment allows them to develop, but our environment can also impact their development — strengthening some functions we may not have used as quickly on our own. The functions we share with our parents are probably strengthened the quickest, because we see and emulate their behavior as children. So yes, I think environment, parents, and siblings have a lot to do with our development.
Ahhhh, so that explains my crazy urges to just get in the car and drive. It’s not the “norm” for an ISFJ, but travel was a great part of my life as a kid and I miss it. Boy, do I miss it. And yes, I am chronically late. No amount of planning seems to get me anywhere completely on time, unless I left a half hour early. Maybe I should try that.