Law professor Eugene Volokh endorses a couple of court decisions that give joint child custody rights to non-parents. He says that this is good policy because they apply of the “psychological parent doctrine” and the “best interest of the child” (BIOTCh) standard.
In a N. Carolina case, a mom's lesbian lover had adopted the child, but the court later ruled that the adoption was invalid. Nevertheless, the state supreme court said that because the mom had foolishly let the lesbian lover act like a parent, the mom had relinquished her rights, and empowered the family court judge to do whatever he pleased.
Volokh acts as if there is some sort of justification for this decision because of psychology or child development, but there was no such evidence at all. The court did not make any finding about who was a “psychological parent”, or how the child might actually benefit.
A comment explains what's wrong with this decision by saying, "I shouldn’t ever have to convince the court that my sister is a drug abuser to decide to keep my children away from her."
That's right. The state has a procedure for assigning parental rights to non-parents. It is called adoption. Unless there is a formal court-finalized adoption, then the parents should retain all of the parental rights. The courts are usurping the rights of the parents for the purposes of some grand social experiments, and I don't see any good coming out of it.