Комментарий к Берешит 41:50

בטרם תבא שנת הרעב BEFORE THE YEAR OF FAMINE CAME — from here we learn that a man must practise continence during times of famine (cf. Taanit 11a).

בטרם תבא שנת הרעב, seeing that Yaakov arrived in Egypt at the beginning of the second year of the famine and he died at the end of seventeen years of having lived in Egypt, he said to Joseph prior to his death: “the two sons of yours who were born before I came i.e. Ephrayim and Menashe, will be to me as Reuven and Shimon.” Any children of Joseph, and he had such, who were born to him after his father arrived in Egypt would be considered as regular grandchildren of Yaakov in respect of the eventual parceling up to the tribes of the soil of the Holy Land. (48,5-6).

וליוסף יולד שני בנים, Two sons were born to Joseph, etc. The Torah includes this with what has been recorded before about Joseph's remarkable achievements during these seven years. The names Joseph gave his sons are proof that he was well pleased that G'd had let him forget his previous problems and had also made him fruitful. The word "fruitful" includes both having children, amassing wealth and being honoured.