He was the son and successor of Matthias I and Bertha (also called Judith), daughter of Frederick II, Duke of Swabia.

His mother wished for her second son, Frederick, to succeed and so Simon was forced to convene an assembly of the nobles to confirm his succession.

He was in turn forced to recognise certain feudal privileges and create the Estates of Lorraine, a form of parliament.

The war lasted three years until the Treaty of Ribemont, whereby Simon retained the southern, francophone, half of the duchy and Frederick took the northern, germanophone, portion.

He married Ida (died 1227), daughter of Gerard I, count of Mâcon and Vienne, and Maurette of Salins.