[{"_id":"1","name":"Grandma"},{"_id":"2","name":"Mum","parentID":"1"},{"_id":"3","name":"Uncle","parentID":"1"},{"_id":"4","name":"Kid","parentID":"2"},{"_id":"5","name":"Sister","parentID":"2"}]

db.collection.aggregate([{$match:{_id:"3"}},{$graphLookup:{from:"collection",startWith:"$_id",connectFromField:"parentID",connectToField:"_id",as:"ancestors"}},{$project:{_id:0,ancestors:1}}])