Based on the context and the answer, generate a question. 

Context: She told me she is being accused of having an affair with a very close family friend . Now the wife called my sister and was yelling at her , then called my sisters husband . He ( BIL ) texted my sister and just wrote , " The cat is out of the bag " My poor sister . Though she never came out and said it was false , I really did not want to know the answer .

Answer:

They are involved in infidelity .



Why is the family friend 's relationship strained ?