Question: When was John De Vere, 12Th Earl Of Oxford's father born?
Sentence (from "Robert de Vere, 3rd Earl of Oxford"): In 1206- 7 Isabel and her sister Constance were co-heiresses of their niece, another Isabel de Bolebec, the countess of Oxford by her marriage to Robert's brother, Aubrey de Vere, 2nd Earl of Oxford.
Relevant evidence: No