What groups joined together to form the "Young Turks"?

Answer: All revolutionaries against the Sultan.

Young Turks was a Turkish nationalist and reformist party of the early twentieth century, whose leaders rebelled against Sultan Abdul Hamid II.

This political movement of a liberal, westernizing and revolutionary nature, sought a constitutional regime and the improvement of the situation of Christians that inhabited Turkey.

In addition, the revolution they led restored the Parliament, which had been suspended by the Sultan in 1878.