Marriage with Françoise de Dinan
It is known that after he had, for financial reasons, let his son Guy XV's engagement to Françoise of Dinan drop in 1440, in favour of Gilles of Brittany. Guy XIV once again abused the young age of this same son, making him break off another engagement to her, when she became the widow of Gilles of Brittany, and engaged him at 45 years old in February 1451 at Vitré, Françoise of Dinan (died 1500), baronne of Châteaubriant. Guy XIV had no rights on the barony of Châteaubriant.
The Vatican archives contain two solicitations to the Holy See on this occasion, by Guy XIV and by his son. The inquiry concerning François-Guy de Laval, fils aîné de Guy, comte de Laval, seigneur du Gavre dates to 23 July 1450 and is addressed to the bishop of Nantes. He begged, for canonical reasons, for an exemption from parental kinship, and from the ban on marriage between a woman and the father of someone to whom she had previously been engaged. The mandate of dispensation for the marriage of Guy XIV and Françoise of Dinan said to be of Thouars from her mother's name, and for their absolution from certain bans, is dated 17 December 1450 and addressed to the bishop of Vannes.
The Vatican archives mention once more mention the comte of Laval and Françoise of Dinan his wife, in their founding of a psallette (choir school) at the Madeleine at Vitré, on 19 May 1453.