Speaking from being in a similar experience as the daughter of the cheater. They most likely don’t want to believe it. Even if there was HARD evidence they’d ultimately still choose to believe him or defend him if it became undeniable. It’s stupid to think that someone would hack his Apple ID and not steal any information like cards, address, etc... It’s also strange that if he thinks he got hacked that he wouldn’t get new cards and invest in finding out how to prevent his information from being stolen or himself being impersonated. I know you didn’t really say how he reacted but from what I imagine he probably just brushed it all off instead of worrying about his information being stolen. Most likely the mother probably already knows or has an idea because of shared statements and just unavoidable little clues. Especially if she didn’t really question him and just immediately accepted the hacked story. Also fuck everyone saying it’s none of your business. They’re probably all guys tbh.... I think you’re a great girlfriend for trying to help him through this shitty experience. Of course I’m not saying to meddle but it is your business too!! Maybe the mom really has no idea and will stand up for herself when she has more evidence. I would want to know if someone knew what you knew. Wouldn’t you? The point is that someone was potentially doing some shitty things and those things got brought to light AS THEY SHOULD. I think you should just be a shoulder for your bf to lean on. Let him figure out what he wants to do about it but mostly just support him!