i assume they were told about the car accident & that she passed away on the spot. they had only accessed her at the funerals in south korea (while she died in the us) and at that point there was nothing left to see of her, so they wouldn’t be able to know the truth unless they looked through the med result papers and i don’t think that’s what they were thinking about back then. since jiwon was in the usa and jungkook resents that whole country (+ jiwons bff literally Broke His Heart in Hawaii and i don’t think jungkook wanted to see any of them anymore) and his dad is also busy at work, i think their only way of communication was through the phone and it wasn’t that hard to hide it. besides, she mentions that her relationship with dad and jungkook was complicated: sometimes they were super close, sometimes they were not. i can assume dad and jk didn’t think much of the distance between them—they thought they would have more time to make up with jiwon. and sometimes the cancer patients seem Fine until the very end, only the last few weeks when it gets really bad and then really Good all of a sudden, and then gone. life. just unfortunate circumstances and jiwon’s well orchestrated plan of her life and aftermath of it. 🫂