My son has had his daughter 3 nights per week since birth. She will be 3 next week. He has an amazing bond with her. This has up to now been a mutual agreement between himself and his child's mother. Lately, the child's mother has tried to reduce this contact.
My son pays regular child maintenance. He also provides everything for his child when she is in his care ie clothes, shoes, toys. Up to now it's very much been shared care.
The mother and her partner want DGD to stay less nights per week. My son has disagreed and this has lead to the mother withholding contact when she chooses.
We have come to the realisation that things are not going to get better and unfortunately he needs a better arrangement for the sake of his child who is being used as a pawn 
We really don't know where to start. His name is on the birth certificate so he does have parental responsibility.
Can anybody advise on what causes of action are open to him. He really didn't want to have to go through the courts but unfortunately it seems inevitable. TIA