Record record record.
Record the conversations with her
Record that she is loving without any harm and willfully
Record everything even if you think it is a small thing.
Not a lawyer.
But seen a lot of things that make me not trust other people
So make sure you have all the facts on record.
If it is not recorded then it’s not there(for male)
Please be respectful and no out bursts.
Calmly stay away from her.
Donot share the same house too.
Stay separated;
Be with your cousin!!! And tell him it is end of marriage not life!!
Call him and visit him.
Make sure he gets help from a professional too to handle this mentally.
It takes a huge toll on him.
PS: not legal advice but I wanted to say out loud to take care of your brother!!