Person A can make a reservation for person B from A's points. In fact, it's often better to do that if B doesn't fly much. No transfer needed, and if cancelled they go back into A's account. That way A can do the paid travel and shoot for status. In many (most?) families, one person tends to accumulate the bulk of points anyway.

I have more than one email address, and I "let" my toddler son use one for WN purposes. He's 16 now. I think I used my cell number for him. Might be time to edit his profile, except that I monitor the FF stuff for my family.

You could probably make up a phone number. I cannot recall any reason WN would have needed it, or checked, or cared.