To show issues linked to the issue you can use the following code snippet:

#foreach ($link in $!issue.fields.issuelinks)
    	
        #if ($link.inwardIssue)
           $link.type.inward 
           $link.inwardIssue.key
        #end

        #if ($link.outwardIssue)
           $link.type.outward 
           $link.outwardIssue.key
        #end
        <br/>

#end