Which all nodes will qualify as an ancestor?
The root-2 is an ancestor of&nbsp;11 (it's the great-grandparent) but you're asking about the&nbsp;2 on the left, which is not an ancestor. There is no directed path from that node to&nbsp;11 since the left-2 has no outgoing edges. Paths must respect the direction of the edges.  Siblings are not ancestors for the same reason.

(Sometimes, we want to talk about a path that ignores the edge directions. These are usually referred to as something like "paths in the underlying undirected graph".)