That means bringing a third person into the mix, therefore becoming a triangle. Instead of two people communicating directly, now you have added a third as a conduit. This is not the healthiest method of maintaining a relationship. Grandparents will try anything to regain access to grandkids and if it means soliciting another person who may have contact with the caregiver as an ally they will do so.
Eventually this will backfire because interpretations can get misconstrued. It’s best to go straight to the source and refrain from involving others.