Career
Blanche was firstly betrothed to Otto III, Count of Burgundy. The marriage contract was signed on 16 January 1236. However, the engagement was broken.
However, John renounced the claim after Margaret of Bourbon bore Theobald two sons.
John and Blanche had eight children:
John II, Duke of Brittany
Peter of Brittany (2 April 1241–Paris, 19 October 1268), Lord of Hade
Alix of Brittany, Dame de Pontarcy
Theobald (1245–1256), died young
Theobald (died soon after birth)
Eleanor (1248), died young
Nicholas (1249–1261), died young
Robert (1251–1259), died young
In 1270 Blanche founded the Abbey de la Joie near Hennebont. She was later buried there.