Who is Sheikh Mahmoud from Woman at Point Zero and what is their importance?

Firdaus' uncle's wife is Sheikh Mahmoud's niece, and she convinces her husband to marry Firdaus to him because he is a virtuous man with a large pension and no children. He is much older than Firdaus, and his eyes always watch her. He has a large swelling with a hole in the middle on his chin under his lip. Sheikh Mahmoud begrudges Firdaus any food and beats her for wasting scraps. When she runs away to her uncle's house, Sheikh Mahmoud beats Firdaus with a stick and rapes her, causing her to run away to the streets.