Who is Mr. Sousa from Welcome to the Monkey House and what is their importance?

Mr. Sousa is in the waiting room with Heinz at the beginning of the story. The nurse comes out to inform Mr. Sousa that his wife has delivered a baby girl, their seventh girl. Sousa is upset that he has been denied a son, yet again. It is implied that Sousa is a large man, and he is described as a "sullen gorilla." When Heinz sees him again at the bar, Sousa is jealous of Heinz's baby boy. He, along with the bartender, lament their many children and ridicule Heinz for looking on birth as a miracle. Sousa finally abandons Heinz to talk to the bartender about baseball.