The nodes in the node tree have a hierarchical relationship to each other.
Merge with DOM - (Node) Tree
An element A is said to be preceded or followed by a second element B if A and B have the same parent node and there are no other element nodes or Text nodes (other than DOM - Text (node)) between them.
A node is the only child of an element if that element contains no other nodes other than:
The terms parent, child, and sibling are used to describe the relationships. Parent nodes have children. Children on the same level are called siblings (brothers or sisters).