Sadly, in our very small circle of friends....one couple has been affected by infidelity via FB posts between her husband and another woman...an old high school friend.
How do you interact in this? Not really sure. The sentence in the FB post said something like "I can make it to where your wife never finds out about us" his response was "how?".
EA for sure, I suspect due to some wierd motives for going to the town she lives in, that he is active and it is PA...but don't know for sure. I am not really close to this guy, but my wife is close to his wife.
Actually...this guy is one of the men I know who I really didn't want to hang with. Something about him was just not my cup of tea.
His wife is settling for less....much like I tend to do. I feel for her. But her being a woman and me being a man....I just don't think I can reach out to her.
With regards to your question.....
Would you let your brother keep doing meth if you found out he had THAT destructive habit? Making THAT destructive choice?
Love.....I had some wacked ideas of what that was pre-A, and so did my wife.
To confront your brother about his destructive choices (provided you know he is having an A) would be the loving thing to do. If he is, he is committing a sin. A loving thing to do would be to bring this sin to his attention and offer to support him if decides he wants to stop his destructive choice.
If he chooses to get defensive and deny what you know to be true....you have done all you can. The loving thing to do is to step back. Adultery seeps into all it touches. 4 deadly A's are adultery, addiction, abuse, abandonment.
At that point you can, out of love for both him and your SIL, turn and offer comfort to her. Help her break out of cycles that would enable her to be further hurt by the sitch.
Love Must Be Tough by James Dobson has whole chapters on what love looks like when you are in a hostile situation, such as knowing a brother is committing adultery.
I would highly recommend getting it and reading it. It was one of the first books I read as I struggled to understand what I needed to do.
Left to my own accord, I would most certainly have enabled our destructive cycles to repeat.
God is with us all.