PROHIBITED DEGREES OF RELATIONSHIP
Extract from Manual on solemnization and registration of marriages

It is pointed out: 

1. that a man may marry the sister or any female relative of his deceased or divorced wife, except an ancestor of descendant of such wife; and
2. that a woman may marry the brother or any male relative of her deceased or divorced husband, except an ancestor or descendant of such husband after Iddat (waiting period).

 As a guide it is mentioned that it is not lawful for a man to marry any person mentioned in column (1) or for a woman to marry any person mentioned in (2)