Question

Who formed the first and second Estates of French society

Answer 1

the Louis 16th make this society and in that clergy and nobility

Answer 2

Clergy and nobility formed the first and second estates. 
The clergy and nobility did not have to pay any taxes.

Clergy was the group of persons who were invested with special functions in the church,e.g. fathers, and other members of the church.

Nobility was hereditary and hence a person could get nobility by birth.