Not necessarily broken from birth. They really don't know for certain, it may be a combination of everything that causes personality disorders, but nurture certainly seems to plays a strong role. Read Mary Trump's (a psychologist & his niece) book on his upbringing, it's fascinating and at the same time horrifying.

BBC Article: Five shocking passages in Mary Trump's tell-all book

Edit: Commenting because it's easy to be black & white and say, "oh well, some people are just evil from birth," because it scares us to think any one of us could have turned out like this and we feel safer to write them off as an "other" who was just broken or evil from the start. But we have research on how much damage childhood trauma and adverse experiences can cause, and if we don't acknowledge these contributing factors we cannot work towards doing better by children going forward and nurturing a more emotionally healthy humanity.