Dilemma

This was quite confusing as I think it is to you to? I think it must be told. It is wrong and should come to the open.

I think that family sounds very amorous. If you tell somebody that their wife or husband is cheating you need to have cast iron proof and also to be prepared for the possibility that they may not want to accept the truth of what you are saying. This could cause them to "shoot the messenger" - even your own brother. By telling her brothers that their wife could be cheating she could also break up the family.

Having said all of the above, I think that each case is different. If it were me I would most definitely not want my brother to be made a complete fool of. If he was blissfully unaware that his wife was making a fool out of him by shagging someone behind his back, I would take a great big deep breath and tell him, with the proof of course. But if your friend's brother and his wife are always fighting and cheating etc maybe she should leave well enough alone, let them work it out themselves, not add fuel to the fire.

But this does not answer your question - yes blood is so much thicker than water, she has a duty to her brother more than her sister in law - hypocritical I know but family is always going to be family. This particular family sound like they have a lot going on!!uses