I got a rejection because one of the parent's of the minor model was  the witness of the release while the other signed the release on behalf of the kid. I am not so sure  if they have a legal  base  to implement such a rule

I can understand why they are being strict about the image quality but I don't see much use why they (most microstock agencies in general) being too fussy about  the paperwork. I like the way alamy works best. they don't even ask you to upload a  model release knowing that it will be  the photographer that is responsible of all the info they provide.

 I'd like to hear your opinion too.

thanks

That doesn't sound right to me.  I have never heard that rule at any of the sites.  Try contacting support.

If the parent is signing on behalf of a minor their signature will have to be witnessed by a third party. 

If you mean that one parent signed and another witnessed, I don't think that a legitimate reason for the MR to be refused.  Just because the last name is the same does not even mean the witness is a parent.

thank you very much everyone for your input.

I recently had a rejection on IS because the witness signature did not match the printed name. I resubmitted the image with explanation in the description that the signature is not in Roman alphabet so it cannot match the printed name. The image was rejected again with the same reason. After a couple of phone calls, emails, and repeated MR submissions due to their server faults, my image got back to pending state for a while, and then they approved it after a couple of days. Luckily it ended well, but it was quite a hassle. It amazes me in what details they go when looking at the paperwork.

And just because the last names are different does not mean they both are'nt the parents ...

true,but what is wrong with it even if they both were  parents.

You can't witness your own signature. Technically you need three people to sign the release. Photographer, model (or guardian) and witness. Some sites will let you be the photographer and the guardian of a minor but the witness must always be a different person.

thank you azurelaroux  for your response and suggestions.I appreciate it.may be my first post wasn't so clear as English is not my mother tongue  to be more precise yes the MR into question was signed by three persons,the photographer,one of the parents   and the other parent as the witness and the rejection reason I was given was that the parents can't be the witness.

but the point I am actually try to make here is that there is not much use dealing with so much paper work here like you mentioned above it is the photographer who should be worried about having a valid MR. this kind of rejections only cause delay of approval process (and it affected  my approval rate negatively which has certain impact on DT search engine)I can re-upload the files with a new MR but that is not the point here I just don't want to get ambiguous rejections because of  model releases. 

I sometimes get MR rejections from IS because the MR contains typed-in information (e.g. names, addresses, dates).

,ironically once I had a file rejected because the  MR was hand written and they didn't find it formal enough.....

I think all the micros require the photographer/guardian at a minimum. I know that IS, SS, FT, DT, CC, 123 and BigStock have all accepted my releases that were done this way. Alamy doesn't look at the MR so it doesn't matter how you do it. That said I think most prefer that it's 3 different people.

 I have also had a mother sign as guardian with a different last name as the minor an it was never questioned by any site.
  I would contact support at the site and ask why it would be rejected.

I got my kids MRs through, with me signing as both photographer and guardian, and my husband signing as witness. They have a different last name than me, maybe the reviewers got confused.