As mentioned by DarkBee and melvio, the question is very vague and needs clearer specification.

That said, what you are talking about is either a so-called ragged hierarchy or an unbalanced one, or both. It's impossible to say from the description provided. If a hierarchy has no children the drilldown will not be rendered by default. If you do have children the drill-down will be rendered. Having children but stopping the drilldown is non-sensical with regards to how hierarchies work.