Formal statement to specify mother and son relationship

[bigC]

When a person writes a letter to authorize his mother to collect a document from the authority, e.g.

I, xxx authorize Mrs. yyy, (formal statement to specify the mother and son relationship),…, to collect the document on my behalf.

What is formal statement to specify mother and son relationship?

 

[tedmc]

I, xxx, authorize my mother, Mr yyy, to collect document zzz on my behalf.

Just say that she is your mother.