She was also the heiress of Escalona, Villena, Peñafiel and Lara, as well as Lady of Biscay.

[1] Her mother Blanca (d. 1347) was a descendant of the lords of Biscay and of Lara and of Alfonso X's eldest son, Fernando de la Cerda.

On 27 July 1350 Juana's brother and guardian, Fernando Manuel of Peñafiel, married her to Henry, an illegitimate son of Alfonso XI.

[1] In 1361, on the death of her niece Blanca, daughter of her brother Fernando Manuel who himself had died in c. 1350 without other children, she inherited the Duchy of Villena, Escalona and Peñafiel.

When in 1381 she died and left her inheritance to her son, it was finally united with Castile, and ultimately Spain.