Best interest

In reality, it comes down to who has the best of the child at heart. As a general rule, I would say the parents given their investment. One can always find the exceptions to the rule, there will always be abuse and poor parenting, but I would wonder about the ratio of adequate vs bad parents compared to the foster care system.

My wager is those with more invested come out on top.

I love this quote from former Supreme Court Chief Justice Warren Burger as highlighted on ParentalRights.org

The law’s concept of the family rests on a presumption that parents possess what a child lacks in maturity, experience, and capacity for judgment required for making life’s difficult decisions. More important, historically it has recognized that natural bonds of affection lead parents to act in the best interests of their children.

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The statist notion that governmental power should supersede parental authority in all cases because some parents abuse and neglect children is repugnant to American tradition.

Show me a government program that is efficient, effective and under-budget. Then we can talk about the government's role in raising children.

But the government intervention isn't always about the best interest of the child, but more often in the best interest of the state.