Support The Krupp Family is a unique decision for 
Prussia, 
North German Federation, and 
Germany.
The Ruhr area has been booming with industrialist and miners trying to make a profit because of higher coal demands. One such industrialist is Friedrich Alfred Krupp, who was the head of Krupp family. The Krupp family had cooperated with The Prussian military by manufacturing weapons and industrial goods like steel.
You can enact the decision if you have enacted Encourage The Ruhr Boom decision, have at least 500 industrial points and have researched Cheap Steel, Iron Breech Loaded Artillery, and State and Government. Also, Germany has to own the provinces Kleves, Dusseldorf, Aachen, Cologne, and Siegburg with a steel factory in the Nordrhein region. Prussia starts with all of the provinces in question.
Once enacted, you will have the best tech school in the game. This essentially makes your research rate one of, if not the highest, in the entire world. It also gives 5 prestige.
Ingame description
A peculiar Military-Industrial complex is emerging in the now heavily industrialized Ruhr-area, where several leading industrialists, notably from the Krupp family, are working together with Prussian Army & Government officials to develop, in coherence with Prussian state ideology, our military and industrial capabilities. Voltaire has said of Prussia that it is an army with a country, and nowhere is this more true than in the Ruhr.