Real category_count

I’m wondering if there’s a way to display a category’s real category_count, by including the category_count of its child (sub) categories? This request is somewhat similar to this support post, but that one only tells how to display a category’s post count. In other words, I’d like to display

Parent Category (10) >> Child Category (4)

where the 4 posts in the child category are included in the 10 posts in the parent category (which in turn means that the parent category only really has 6 posts directly assigned to it).