[{_id:"Parent1",kids:[{_id:"Test1",grandkids:[{name:"Blah"}]}]},{_id:"Parent2",kids:[{_id:"Test1",grandkids:[{name:"Bloh"}]}]},{_id:"Parent3",kids:[{_id:"Test2",grandkids:[{name:"Bloh"}]}]}]

db.collection.find({kids:{$elemMatch:{_id:"Test1","grandkids.name":"Bloh"}}})