Or HaChaim on Genesis 41:50/אור החיים על בראשית מ״א:נ׳

1 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.

2בטרם תבוא שנת הרעב, before the year of famine arrived. Taanit 11 derives from here that it is forbidden to maintain marital relations during a famine. We can conclude from the fact that the Talmud uses the example of Joseph [the words "before the arrival of the year of famine"] to deduce this ruling, that it is applicable only to people who have not yet fulfilled the commandment to be fruitful. Joseph had already fulfilled that commandment, ergo he could not have marital relations during the famine. Had he not had children yet, the fact that there was a famine would not have represented a halachic hindrance to his having normal marital relations during that period.

3Keeping this in mind, the question raised by Tossaphot in the Talmud about how Yocheved could have been born during the descent of Jacob's family to Egypt, seeing the famine was in full swing at the time, becomes moot. Tossaphot is at pains to explain that the rule was not a legal one but only a pious practice. This appears unacceptable seeing the whole rule is based on scripture. Besides, the Torah testifies to Levi's piety in Deut. 33,8, suggesting that of all the sons of Jacob he was the most pious. Even though the statement in Deuteronomy refers to the descendants of Levi, i.e. the branches, it is most certainly applicable also to the root, i.e. to Levi himself. Inasmuch as Levi did not yet have a daughter at the time, he was at liberty (compare Yevamot 61 and Even Ha-Ezer 1) to indulge in normal conjugal relations with his wife.

4Moreover, the prohibition of conjugal relations applies only when the Jewish people experience the pain of a famine. Famine amongst the Gentiles has no bearing on Jewish family life. Inasmuch as Jacob was known to have a sufficient supply of food (compare Taanit 10) and he only sent his sons to Egypt for appearances' sake (so as not to arouse the envy of his neighbours) as we know from Rashi on Genesis 42,1 למה תתראו, Levi had acted one hundred percent within accepted Jewish norms. While it is true that there is a statement in Bereshit Rabbah 91, that Jacob's family did not even have any barley left, that statement refers to the second year of the famine. During the first year they certainly had enough grain left and Levi had every right to sleep with his wife. They did not have to refrain from conjugal relations on account of Joseph. Joseph was only an individual and the rule applies only to when a community is in economic straits. It is possible that Joseph refrained from conjugal relations with his wife during the famine because he knew that his family in the land of Canaan was suffering from the famine (the first year before they came to him).