In an ideal world, people would have kids when they were ready to care for them, from infancy to adulthood. They would face no struggles, and kids would face no hardships. Unfortunately, we don't live in an ideal world. Children are born to parents who are unable to care for them. They end up abused or in foster care, or in best case scenarios, adopted by families who can show them the love and support they need. When parents aren't able to care for their kids, grandparents can be the next best option (assuming they are in the position to care for the kids). But can grandparents sue for custody? It's not such a simple process, and in the eyes of the legal system, it's not always so cut-and-dried.
In the eyes of the legal system, parental rights will be considered the priority, and in most cases every attempt will be made to keep children with their parents. When that's not possible and the kids are better off in someone else's custody, grandparents can (in some states, depending on the statute) sue for custody.
In cases where both parents are living, grandparents can sue for custody when both parents have been deemed unfit, there's documented abuse or neglect in the home, there are drugs or alcohol in the home that endanger the kids, the parents' mental health makes them unfit to raise the children, or both parents consent to sign over custody to the grandparents.
When one parent is unfit and the other can't or won't take custody of the kids, a grandparent can sue for custody, as well. However, in the eyes of the court, grandparents aren't given special consideration over other options; it can help bolster the grandparent's case if they've been caring for the children for at least a year prior to seeking permanent custody.
Now, as you might have guessed, the circumstances in which a grandparent can sue for custody and be granted custody by the legal system are limited. So when can't a grandparent sue for custody? In cases where the grandparents don't agree with how the parents are raising the children, or disagree about certain aspects of their parenting, a judge would likely not remove the children from their parent's custody. It's also important to keep in mind that granting to custody to grandparents does NOT terminate parental rights, and custody arrangements can be changed when circumstances change.