Again, we are talking of who are Han people and what are Han´s cultures and custom.
As KirovAirship says, (and correct me if I´m wrong) Han people share a common cultures and custom, you can say a single cultural umbrella. Besides Ancester worship, Confucism and Taoism,
Buddhism is another character of the Han. The Han people are heterogeneous, they belong to different ethnics and speak different Chinese dialects with mandarin as preferred languague. But first and foremost Han is not about DNA, nations, languages, ethnics or races. It is not about citizenship, either. At least no directly related. Well, China is the home of the Han, and most of the Han have a common DNA trait. No doubt about it.
How about the Jing people in China? why this ethnic minority, which immigrated from Vietnam hundreds of years ago is seen as minority and not Han? I can´t tell you, but I assume it is a matter of politics. Perhaps KirovAirship can tell us why? In this point, we see Han concept is a bit cloudy.
The concept of Han is reminds me to that of Western countries, called "Christian traditions". It is somewhat similar. As you know the
European Union (
EU) is an
economic and
political union of 28
independent states, and all of them share Christian traditions. Germany is a part of it. France, too.
What are Christian traditions of these western countries? well, they are a set of similar traditions, religions (most Christians), cultures and custom which are developed and evolved with the times. For instance the French, the Germans and the Greeks think they belong to a family.
Here is a graph showing different christian traditions, but one common root:
Since decades (50 years), Turkey is trying to become a member of this family, they fail. Why? Because the Turks are Muslims. They have different cultures and custom. Others don´t want them.