Once two or more trees have been merged-it is up to everyone in the tree to assist with merging duplicates. Removal of these duplicates may result is loss of lots of hard work.
Therefore, you should merge those. To do so, you may use the ‘Move this Person’ button found in the 'more' link of a node on your tree. This will add the node to the 'Move These People' tray, found on the side of your Tree view. Then drag the node onto the second person to whom he or she is related and select the appropriate relationship.