If a man trusted his family, he would give them access to his wallet. And then he would not have been poisoned by drugs, and he could have died.
Probably not enough trust to literally hand over the exchange account's credentials or the wallet's private keys, but trusted enough to be live in the same home/room and probably give access to the phone's pin. Obviously the son still needs to have access to the phone itself, so this is the solution he thought of.