Seems like a neat idea actually. Just be careful on choosing whom to give a piece of the passphrase as it will be valuable in times of need. If in case one part of the passphrase is lost, creating the whole passphrase and safekeeping it would save you and your family in case one part was lost.
thats why you use static data, like a social security number or date of birth. so its readily available.. but without having to actually write down the data itself.
you then do not explain what category of data you are using of the individuals, you keep that safe and locked up in a will. you can even have a safe deposit box
which contains the order in which the splits should be positioned and keep that in another location for extra safety.
but the main bit is.... if you cannot trust 4 people in your life. then maybe they do not deserve to be your beneficiaries, and you should choose a charity or just a couple people to receive the inheritance