 As a child, Isabella was sent to the household of William and Elizabeth St Omer, which also included Isabella's older brother Edward and younger sister Joan.When she was just 3 years old, her father attempted to arrange a marriage between Isabella and Pedro of Castile, the Castilian King's heir; however, her younger sister Joan later became Pedro's betrothed, dying before they could actually marry.Described as being over-indulged, wilful and wildly extravagant, Isabella – unusually for the times – remained unmarried until the age of 33.