How would you describe Eric's position in the family?

Eric is the son of Arthur and Sybil Birling. Brother of Sheila Birling. Eric is in his "early twenties, not quite at ease, half shy, half assertive" and, we discover very early in the play, has a drinking problem. He has been drinking steadily for almost two years. He works at Birling and Company, and his father, we presume, is his boss. He is quite naive, in no way as worldly or as cunning as Gerald Croft. By the end of the play, like his sister, Eric becomes aware of his own responsiblities.