I agree that my BIL should be the one to tell my sister, but I'm sure he won't. My drive to tell her is that I believe she needs to know, but more importantly, this would halt him from trying to message my wife anymore. I've thought of just confronting him without letting my sister know as well.
M 17 years 3 kids EA start 2010 ILYBNILWY 1/2014 PA 1/2016 Bomb drop 2/2016 Renig on Bomb drop 4/2016 Living as roommates, EA continues