When his brothers first stood before Joseph in Egypt, who recognized whom?

Answer: He knew them; they didn't know him

Joseph recognized his brothers but treated them as strangers and spoke harshly; they did not recognize him.

“And when Joseph saw his brothers, he recognized them, but he treated them as strangers and spoke harshly to them. “Where have you come from?” he asked. “From the land of Canaan,” they replied. “We are here to buy food.” Although Joseph recognized his brothers, they did not recognize him.”— Genesis 42:7-8 (BSB)