My Beloved is "Auntie Vice" to her nephew. His parents wanted him to have an Auntie Vice and Uncle Vice. The Vices were to be the people their son could go to when he had awkward questions about stuff you just don't want to talk to with your parents (sex, drugs, etc.).
Uncle Vice has dropped out of the picture but her nephew loves his Auntie Vice. She always gets the best toys and will answer any question he wants. In fact, he recently asked what tea bagging was. So she told him. (His parents were really happy she handled that one - and yes, it was not about politics.)
She finds this profoundly rewarding and has a special place in that child's life.