[{id:1,fname:"Barry",lname:"Sullivan"},{id:2,fname:"Sarah",lname:"Bailey"},{id:3,fname:"Drake",lname:"Barry"},{id:4,fname:"Another",lname:"Sullivan"}]

db.collection.aggregate([{$facet:{first:[{$match:{id:1}}],others:[{$match:{$expr:{$ne:["$id",1]}}}]}},{$unwind:"$first"},{$project:{matches:{$filter:{input:"$others",cond:{$eq:["$$this.lname","$first.lname"]}}}}}])