My son and his ex share 50/50% legal custody of their children. Does the Dr.have to keep both parents informed?

Last year my 1 y.o. grandson ended up in critical care because mom refused to listen to dad about their son's illness. My son took the baby to the ER. He was diagnosed with RSV, asthma and bronchitis and admitted to the hospital for 1 week, 3 of those days in critical care. We almost lost him. The child is... show more Last year my 1 y.o. grandson ended up in critical care because mom refused to listen to dad about their son's illness. My son took the baby to the ER. He was diagnosed with RSV, asthma and bronchitis and admitted to the hospital for 1 week, 3 of those days in critical care. We almost lost him.
The child is sick again and the doctor (that mom uses) refuses to call my son back with medical information regarding his illness. She claims it's "just a virus" but that's what she said last time and that did not turn out well. Last Wednesday during visitation my son took the baby to another doctor for a 2nd opinion. This doctor wants him on antibiotics since he does not seem to be getting better. Mom refuses to give the child his meds and dad is scared to death this is going to be another life-threatening issue. Anyone know what the doctors obligation is? Please, don't be rude. There's enough of that in our life.
Update: I appreciate your answers. I agree that more than one doctor can be dangerous but when a child is misdiagnosed and mom continues to to take the child back to that doctor (who has lost credibility), SOMEONE has to make sure this baby gets the proper treatment. Thank you for your insightful answers.
Update 2: My son has made sure the 'other' doctor has received every single note and recommendation (faxed AND sent registered mail) his pediatrician has made, however they have never been acknowledged. I have a phone call in to the attorney who said the doctor must follow the court order and share information.... show more My son has made sure the 'other' doctor has received every single note and recommendation (faxed AND sent registered mail) his pediatrician has made, however they have never been acknowledged. I have a phone call in to the attorney who said the doctor must follow the court order and share information. I'm guessing it's going to get uglier before it gets better.
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