Rashi on Genesis 44:20/רש"י על בראשית מ״ד:כ׳

1ונאמר אל אדני WE SAID TO MY LORD — we kept nothing back from you (Genesis Rabbah 93:8).

2ואחיו מת AND HIS BROTHER IS DEAD — He uttered this untruth out of fear. He thought: if I tell him that he is alive he may say “Bring him to me”.

3לבדו לאמו [HE] ALONE [IS LEFT] OF HIS MOTHER — of that mother he has no other brother.