Nested Hierarchy for Dummies
A nested hierarchy is nothing more than a well defined(super) set which contains and consists of other specified (sub)sets.
A good visual would be the Russian nested dolls.
For example when discussing Living Organisms we divide everything into Kingdoms. Humans are Homo sapien sapiens- Homo being the Genus, with the species and subspecies- are in the Kingdom Anamalia.
IOW the Kingdom Anamalia consists of and contains every level below it. Anamalia being the superset, with Chordata a more refined subset and Primates being a more refined set of Chordates so on down to the species level. Each level being a more refined level of the one above. Each level containing and consisting of the levels below it.
In the Army example we would be classifying the US Army which is broken up into Field Armies, which contain and consist of Corps, which contain and consist of Divisions, which contain and consist of Brigades, which contain and consist of Battalions, which contain and consist of Companies, which contain and consist of Platoons, which contain and consist of Squads & Sections. Squads and sections contain and consist of soldiers. Each level, down to the soldier, has a well defined role and place in the scheme.
Here is the $64,000 question:
In a paternal family tree scheme does the top level, the father, consist of and contain the lower levels?
(If you answer "yes" you are a complete moron and if you answer "no" then you see why a paternal family tree is not a nested hierarchy. You are not a complete moron.)