According to his Vita, written by Braulio, the bishop of Caesaraugusta (modern Zaragoza) roughly a hundred years after the saint's death,[2] Aemilian was born in Vergaja,[3] which is identified with Berceo in La Rioja, where he was a shepherd.

He sought out an experienced hermit in Bilibio,[4] Felix (more usually known by the Spanish form of his common name, San Felices), where Aemilian lived for a number of years.

After leaving his teacher, Aemilian lived as a hermit (perhaps even a gyrovagus) in the mountains or on the historic Roman road which became the Camino de Santiago.

[7] Braulio also recorded miracles that occurred after death of Aemilian, but the fame of the San Millán de la Cogolla monastery dedicated in his memory (and which held his tomb) eclipsed that of its founder.

Because of the monastery's role on the traditional pilgrimage route, representations of Aemilian can be mixed with that of Saint James the Moor-slayer, such as a Benedictine on horseback with a banner and sword.