I know this sounds like a good idea, but let me tell you why it's not. Let's say your [spouse/son/daughter/parent/sibling/significant other/etc.] gets into a car accident, or gets rushed to a hospital with a heart attack or Covid-19, and they need to reach you from the emergency room. (Or the police try to call you, or a paramedic needs to find out quickly if your relative has any allergies to a lifesaving medicine.) But they can't, because you never thought to whitelist a number you had no prior knowledge you'd ever get a call from. And because of that, your relative has an adverse outcome. (Use your imagination.)
I have this exact situation. As much as I try rejecting calls from numbers I don't recognize, I have a 93 y/o mother in Florida, and if I get *any* incoming from her area code, I gird my loins and answer it. Most of the time I wish I hadn't, but there are those occasions when I really needed to react to that call fast, and having the number blocked would have been catastrophic.
So please, think this one through.