In Troxel v. Granville, the court, citing a number of cases under the Fourteenth Amendment, ruled that parent have fundamental liberty children.
In general, courts start with the best interest of the child, or, "even better, will result in harm to the child."
Grandparents bringing action is likely to be bitter.
Resources: www.aarp.org/life/grandparents Trowel v. Granville, 120 S. Ct. 2054 (2000).