Hi,

Thank you for your message.

The reason it is acting this way is really by design behaviour. In the related docs webpart you can specify the relation ship with Current document is on the left side property. You can have it either checked or unchecked which represents which side of relation ship should be used.

What you can you is to place 2 related docs webparts next to each other and then on one check this property and on the other leave it unchecked.

Now you should see all related documents from both sides.

Let me know how that works.

Kind regards,
Richard Sustek