Family Problem

My brother in law (38m) and I (36m) are close. He was having issues within his marriage, with my wife's oldest sister, and ended up telling me it started with finding out our wives middle sister molested his son (12). He told me I can't tell my wife or anyone until things are finalized because HE could go to jail. Why would he go to jail?

We have kids of similar ages and no one told us this. My wife's family still has her at all of the family functions, but my bother and sister in law were never showing up. He said the middle sister in law admitted to it and their son is in therapy. Why would they go to jail for telling anyone? How long does it take to charge someone with this crime? It came to light in April!