Asalam Alikom wa Rahmtuallah Wa Baraktuh.
It has come to my families attention, that one of my male step grandchildren, has been sexually abused by their Maternal grandmother.
The child is only 4 years old, and tells of having being asked to undress, then his grandmother has played with his genitals.
The Grandmother had admitted to her ex husband 16 years ago, that she had sexually abused 2 male children, while she was babysitting them. He at that time did not know the full implications of what she had shared with him.
What should we do now? My step daughter is totally devastated by this. The Grandmother that has done this, to our knowledge is not really a practicising Muslim. Should we confront her, charge her under Canadian law? Our concerns lay in: 1. how many children has she abused in the last 16 years, 2. our need to want to protect any other male children. 3. Long term affects on the 4 year old we just found out about.
JazakALLAH for any help you can give us.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is not permissible to accuse this grandmother of doing this matter to that child with a bad intention, just because the child said so; especially that she is his maternal grandmother. Therefore, you should not confront her with this matter or sue her because of it. It should be mentioned that it is not permissible to resort to man-made laws except for necessity.

Moreover, you should not raise such matter with that child, rather, you should avoid talking about it and not mention this to him, because this may sadden him and cause him negative effects.

The best thing by which a child is protected in general, is by nurturing him on religion and ‘Eemaan (faith), and the parents should be an example for him in this.

However, if it is really known that the intention of this woman was bad, then she should not be left in seclusion with the child, and if there is a necessity for him to visit her, he should be accompanied by someone else, like his mother.

As regards the number of children with whom the grandmother did this, then you should not think about this matter, let alone asking about it. Among the good traits of a Muslim, is abandoning what does not concern him. 

Allaah Knows best.