Isabel was the daughter of Thomas de la Barre but her mother is unknown. The date and place of her birth have not been found.
She had two marriages/partners. Her first husband was sir John Eylesford. They were married, but the date and place have not been found. Their only known child was John (c1350-c1395).
Her second husband was Richard de la Mare. They were married, but the date and place have not been found. They had no known children.