Is my wife cheating me?

[Malini]

I think you are jealous and insecure. Relax.

[Chell]

It is natural and humane to attract the near ere than what is available.
He is hers sisters husband.
He may try for to be nearer. But if you be too nearer and dearer to her, as a wife she may not cheat.
It is your life, she may get ruined. Be polite ans take appropriate action.

[Mary Eggert]

The simple fact is that you are just presuming that she is cheating but in reality you don't know.
She may be cheating, she may not be, the only way to know that is to find out what she's doing and who she's talking to, witch may be a gray moral ground but such is life.
Seek the help of a private detective or do whatever you can legally do to find out for sure, there are also online resources that can help you find out exactly, but be careful with what you are doing so you don't cross any legal or maybe even moral boundaries.

[mandar]

yes she is. Leave her