Finally understood

Martins father was in a relationship with Mrs Ulman, and the fat lady, with green coat,which ballooned around her belly, with large fleshy cheeks and no neck,and pudgy body,with small sharp and blue eyes, was martins mother. As his dad gave him dhoka(cheated on her), so the lady came to kill both of them, so she first targeted martin, then his dad, and then Mrs Ulman.