Ferdinand reigned as jure uxoris Count of Flanders and Hainaut from his marriage to Countess Joan, celebrated in Paris in 1212, until his death. He was born in Coimbra, and he was an Infante of Portugal as the fourth son of King Sancho I of Portugal and Dulce of Aragon.

Dulce of Aragon also called Dulce of Barcelona, was Queen of Portugal as the wife of King Sancho I of Portugal.