My elder brother isn't in the country currently

He is married with two kids

Last year he found out that his wife was cheating on him because her Facebook account was hacked and she had to give him the password so he could help her recover it

When he found out he wanted to end the marriage but the family pleased with him to allow her go for cleansing in the village after much pleas he agreed to allow her go for cleansing last year

Recently,I went over to pay her and the kids a visit and I found out she was chatting with a man that's close to my brother

From their chats,it's obvious they've had sex and she told him to act like it never happened

They do video calls and show their nakedness to each other, although she called off everything with him September this year but they've obviously had sex this year and that's after the period she went for cleansing in the village

I have screenshot of the chats

But I'm confused if I should show it to my brother or not because I don't want my nephew and niece to be a product of a broken home

Cos my brother wouldn't want to continue with the marriage if he finds out she's still cheating

But if I don't open up and my brother returns and have sex with her, he'll fall sick and he might die if she refuses to open up 

Please advice me on what to do

Thanks

From my inbox

Pls advice a sister

My husband demand for sex but I wasn't in the mood due to some stress, I told him I am not in the mood for anything now, in the following morning he came home with another woman having sex with her in my own eye, almost two week now she is still with us, am confuse of what to do, my husband is not talking to me nor eats my food, pls what should I do to save my home.