Anonymous wrote:Wouldn't mom be more embarrassed or upset that her daughter knows about dad's infidelity?
Wouldn't mom rather find out than be kept ignorant and later find out when she tests positive for an STD?
OP, tell dad; show the screen shots you took; tell him that you have to assume his huge carelessness means either he wanted to get caught or he is so arrogant that he figured no one else would ever call him out. End with, "You've cheated not just on mom but on us as a family. I can't unlearn what I've learned, and I believe mom needs to know, at a minimum because you have put her at risk for STDs. You can tell her yourself before (date) but after that day I will tell her myself if you have not. This isn't a discussion or a negotiation. Either you tell her or I tell her but either way she knows."
Script it out and practice before you face him. Don't let him convince you you're imagining things.
You may have to add that if he tries to screw your mom financially you will have to let his lover know their cover is blown and both of them will discover their law firm is aware if how they've abused work travel or whatever. Some law partners wouldn't care but maybe his would....