[{"_id":"A","children":{"aliased":["B"]},"parents":{"aliased":["B"]}},{"_id":"B","children":{"aliased":["A","C"],"related":["X"]},"parents":{"aliased":["A","C"]}},{"_id":"C","children":{"aliased":["B"]},"parents":{"aliased":["D","B"]}},{"_id":"D","children":{"aliased":["C","Y"]}},{"_id":"X","children":{"aliased":["Y"]},"parents":{"related":["B"]}},{"_id":"Y","parents":{"aliased":["D","X"]}}]

db.collection.aggregate([{$match:{_id:"A"}},{$graphLookup:{from:"collection",startWith:"$children.aliased",connectFromField:"children.aliased",connectToField:"_id",as:"connected_authors"}},{"$project":{"connected_authors":"$connected_authors._id"}}])