He was the son of Wilfred the Hairy, Count of Barcelona, from whom he inherited the county of Cerdanya.
His brother Sunifred received the county of Urgell, and his brothers Wilfred II Borrell and Sunyer I received the county of Barcelona.
[1] His sister, Hemmo (Emma), became abbess of the Monastery of Sant Joan de les Abadesses in Ripollès founded by their father.
Miro continued the work of his father, contributing to the ecclesiastical restoration of the pagus of Berga.
He and Ava of Cerdanya had four sons and one daughter: Also, his relationship with Virgilia of Empúries, daughter of Dela, count of Empúries, produced (among others):