In FH if you use the records window to list all of the individuals held in the database if you have the column "relationship to Root" set up, click on this to show the relationships of everyone to the root person. the top ones should show blank if there is no direct relationship (if they don't show right click and select sort ascending).
You can then select any individual and then click on the diagram options either on Both Ancestor and Descendant or All relatives to give you a tree of the links associated with that individual.