
Mostly just his personality. Some people have anxiety. He does verbalize and acknowledge his early losses. Being adopted, he is well aware that his birth mom and dad abandoned him. He takes that loss to heart and is afraid of losing the family he has now. My dad died when DS was 4, they were very close. He spent months and months worried that DH and I would die and leave him. We had to make a pact that even though we all have to die, we will meet in heaven. It did give him some comfort. Even now, he worries, mostly about me. So the things he is scared of in books involve injury or death, which he directly applies to his family.
So the Fortnight commercials show guys with guns. Guns can kill Mom or Dad. Nightmare.
Same with the tsunami, volcanoes, sharks. “No mom, volcanoes can kill you. Do you want to die? I don’t want to lose you.” We just try to work through it and avoid obvious triggers. But irrational fears are..well, irrational.