Dear Nikola,

Further questions:

a) Since Donna, Tod, and yourself are all in the same legal position vis-a-vis Robert, you should all be able to rely on the same single legal opinion.  Would either Donna or Tod be willing to enlighten you as to what your signature would mean, and why you should sign?  

b) Possibly you should comply with Robert's request to sign, as a matter of family loyaty or friendliness.  Obviously, I have no basis for any opinion.
EJM