This property returns a reference to the first sibling of a Node object in a TreeView control.
node.FirstSibling
The FirstSibling property is read-only. FirstSibling returns the first Node at the same hierarchical level as node. The Node returned depends on the Sorted property of the TreeView control. The Child, FirstSibling, LastSibling, Previous, Parent, Next, and Root properties all return a reference to another Node object.