Who is Ahronchik from Tevye the Dairyman and the Railroad Stories and what is their importance?

Ahronchik is a young man in his early 20s who does not work, and is supported by his wealthy widowed mother. Ahronchik becomes friends with Tevye and then meets and falls in love with Shprintze. They are to be married but Ahronchik and his mother go home and the engagement is broken.