He was the son and successor of Gonario II, who abdicated the throne and retired to the monastery of Clairvaux to live out his days.

In October 1163, his brother Peter succeeded Constantine II of Cagliari as his daughter's husband.

He was soon opposed by Barisone II of Arborea, who expelled him from Cagliari, and he fled to Torres and the protection of his brother.

With Pisan support, the brothers invaded Cagliari in March 1164, reconquering the city, and then Arborea in April, where they holed up Barisone in his castle of Cabras.

In 1166, Barisone and Peter travelled to Pisa to explain the bloody reprisals of the citizens against the Pisans in Ottana.