I recently found out that my brother in law is cheating on my sister in law with his ex baby mama.. should I tell her?

Backstory: a friend of mine told me that she saw my brother in law and his previous ex baby mama together… I was so shock with this information and now it’s bothering me for quite awhile now. I know it’s none of my business but I want to tell my sister in law because she deserves to know. Although it’s not my business. I want to tell her anonymously.. SHOULD I TELL HER? OR STAY OUT OF THEIR BUSINESS AND LET HER FIGURE IT OUT ON HER OWN?
I recently found out that my brother in law is cheating on my sister in law with his ex baby mama.. should I tell her?
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