I think it is possible if none of the parents pass the RHD, because RH positive is dominant so if both parents are carriers for RH positive then the child can be RH negative; Dd(carries RH positive) dd(RH negative)
Negative groups will not clump through agglutination. That's why blood with negative RH is able to donate to either positive or negative. Positive RH however, can only donate to another positive RH.
Clumping means agglutination reaction between A-Antigen, B-Antigen, and D-Antigen on the red cell's membrane with the antibodies such as Anti-A, B, and D reagents.
Clumping mean the agglutination(fighting/break down) between the antigen and antibodies... Antigens are present over the surface of RBC and the antibodies are the given serums... If the serum agglutinate the blood them it would be that blood group....