How can i display child terms under parent terms and assigned articles using entity field query?
Term relationships aren't kept in a table that the entity API knows about, so you can't use an EFQ to query them.

taxonomy_get_tree() exists for exactly this purpose:


  Create a hierarchical representation of a vocabulary.


e.g.

$vocab = taxonomy_vocabulary_machine_name_load('foo_vocab');
$tree = taxonomy_get_tree($vocab-&gt;vid);


You can optionally provide a $parent_id as a 2nd argument, to force the root of the tree to a specific term.