Who is Jacob Novak from Bread Givers and what is their importance?

Jacob Novak is Mashah's boyfriend. It is noted that she suddenly has an interest other than herself when she becomes involved with Jacob. He is a pianist and is preparing for a concert. His father forbids him to see Mashah, apparently because of the family's poverty. Jacob first accepts this, then begs Mashah's forgiveness. At this point, Reb says Jacob cannot be trusted and Mashah gives in to her father's demands that she break off the relationship.