Employment Confidentiality Agreement

Can someone sign as a witness, as a parent or family member as they witness the signature?

Depends what for, but they must be at least 18 years or more.

To be a better witness, they must be isolated, but almost all of a witness actually said "I saw this person sign the document." Unless there is some risk that the person would lie about the signature or be suspected of lying, it's not really what they are. The witnesses are rarely called to testify in court, it comes only when one party attempts to withdraw their signature is valid. Very few cases of contract law does not stand or on that basis.

Why not?