Esteos is a country in which the federal government and the twelve state governments share powers. the form of government in esteos is called

This would be federalism.
Federalism is a unique system as it combines one government which is central (that is federal) that is there for the entire country but it is combined with the governments of the individual states of which the country is consisted. This can be seen as a division of power between to different kinds of government but of equal power. The United States is the example of the federalist government.