According to what certain writers have set down in their books, Prior Álvaro Gonçalves Pereira, being both sensible and intelligent, was reportedly an astrologer and a man of great wisdom. Whenever any of his children were born, he dedicated himself to the astrological interpretation of the birth. Thanks to his astrological knowledge he was convinced that one of his sons would always be victorious in every battle in which he took part and would never be defeated. They say that throughout his life Álvaro Gonçalves believed that this talent would be the lot of his son Pedro Álvares, who after his death became Prior of his Order, and with that in mind he always singled him out among his brothers.

Other writers give a contrary account, and this version we find more satisfactory, because they say that in the household of Prior Álvaro Gonçalves there was a widely read and very knowledgeable astrologer by the name of Master Tomás. They record that it was from this man that the prior learned that one of his sons was due to be victorious in his battles and this was Nuno Álvares Pereira.

This is clearly demonstrated to be the case, because, when Prior Álvaro Gonçalves arrived at the palace of King Fernando to deal with certain matters, he begged a boon of the king, namely that he should receive Nuno Álvares as a resident in his household. As this was pleasing to the king, he granted his request. The prior then departed to his estates and made ready to send his son to the Court. Before sending him, he called for Martim Gonçalves do Carvalhal, who was the uncle of Nuno Álvares and his mother's brother. He made him swear an oath that he should never mention to Nuno Álvares a certain matter which he wished to disclose to him. Once he had promised to keep the matter secret, the prior then told him that he was intending to send his son to the Royal Court and Martim Gonçalves along with him as his tutor. For that reason he begged him to assume the responsibility of carefully rearing him, and he assured him that his son would be gifted with great prowess and would always emerge victorious from every battle he joined, provided that he held close to God in all his undertakings and did nothing that was a disservice to Him.