The idea of Jung, I personally think is a good idea, is that we are not tabula rasa (clean slate) but there is an outline of our personality when we are born. That we have archetypes which to a certain degree affect how we are going to develope like a "generalized aim" that allows change in function developement but still has a focus. We try on different ways of finding our personality, whether that is affected by our enviroment I dont that much about. But I would still agree that there is some enviromental developement, like if you have been affected by strong influences from your enviroment. Like if you where brought up with abusive parents your archetype might be emphasized more by the child or completely disbanded. Thats why its difficult to say 100% that its like described above. But if you have had a protective childhood there is a big chance the above is true.
Look at twins. I know two pair of twins that are very much different from eachother because they are not identical twins. I dont know much about identical twins, but i would speculate that in mbti terms they have a close if not the same personality. Like one is esfp other is isfp. Or one is isfj one is infj. Since their archetype and genetic material would be the same but they might mirror eachother but still use functions that are in close to eachothers.
My parents are isfj and istp and my sister estj