As grand parents can we get visitation rights to our 3 month old grandson

My son has been hit on several occanions my his wife, we have wittness this often with the baby between then, when she attact our son we call cps when we learn about her hitting him while he was driving the car over the mountain puting all they lifes in danger.we incourage our son to get a order of protection for himself and the baby. she was violated this order,and my son is now siding with his wife they are both deining us visisation with our grandson. on one occassion she almost droped the baby while trying to hit a visitor in our home, because our son spoke to her, the baby had to be taking from her and she proceeded to chase this girl out of the house and down the lane and at this time she ripped open her sutures line and later had a staft infection we took her to the hospitial for this and also for post parden depression, she took the medicine for about 1 1/2 weeks with no side effects, but reported to CPS she was getting dizzy from it thats why she stopped taking it.They are now in they own apt about a mile away, but deiding us visitation with our grandson we live in Greenwood Lake New York.All we want is visitation with our grandson and to be a part of his life so he can be part of our family, with aunts and uncles and cousins.