Sharing Content document link with grandchild

This is what I have so far:

if(Trigger.isInsert){
        Set<Id> getAccts = new Set<Id>();
        Map<String,String> m_accts = new Map<String,String>();
        for(ContentDocumentLink contDocLink : (List<ContentDocumentLink>)Trigger.new){
            if(contDocLink.LinkedEntityId.getSObjectType().getDescribe().getName() == 'Account'){
                if(!getAccts .contains(contDocLink.LinkedEntityId)){
                    getAccts .add(contDocLink.LinkedEntityId);
                }
            }
        }
        if(!getAccts .isEmpty()){
            Map<Id, Contact> m_accts= new Map<Id, Contact>([
                SELECT Id, ,
                (SELECT Id, Account, category__c FROM Invoices__r  WHERE category__c = 'Date Received')
                FROM Contact WHERE Account IN: getAccts
            ]);
            system.debug('m_accts' +m_accts);
            List<ContentDocumentLink> linkList = [ SELECT Id, ContentDocumentId, LinkedEntityId FROM ContentDocumentLink WHERE ContentDocumentId IN: getAccts  ];
            system.debug('linkList ' +linkList);
            if( !linkList.isEmpty() ){
                for( ContentDocumentLink link : linkList ){
                    List<ContentDocumentLink> links = this.linkMap.containsKey( link.ContentDocumentId )
                        ? this.linkMap.get( link.ContentDocumentId ) : new List<ContentDocumentLink>();
                    links.add( link );
                    this.linkMap.put( link.ContentDocumentId, links );
                }
            }
            system.debug('linkList ' +linkList);
List<ContentDocumentLink> linkList = [ SELECT Id, ContentDocumentId, LinkedEntityId FROM ContentDocumentLink WHERE ContentDocumentId IN: getAccts];