Template query: Advanced section query to get unique items from custom entry type field
Try this:

// Return all ids for your posts' section
{% set postIds = craft.entries.section('blogEntries').ids() %}

// Look for and return employees which have a relation with any of the posts returned in 'postIds'
{% set writers = craft.entries.section('employee').relatedTo({ sourceElement: entryIds }).all() %}

// Loop and display
{% for writer in writers %}
    {{ writer.title }} &lt;br&gt;
{% endfor %}


This will only return a list of writers who have written a post, not a list of all writers but I guess that's what you want..?