Brother is a cheater- do I tell?

[baddabingbongbang]

Name changed for this just in case.
My brother is a serial cheat. He's cheated physically and emotionally with multiple women including close friends of his over the course of about 5 years. He and his girlfriend are both 24 and are planning on buying a house soon. He's treated her appallingly and she deserves so much better than this. He's told my parents that every time she gets close to finding out, he lies and twists the situation to save his own skin, calling her controlling, threatening to leave her etc until she backs down and trusts him.

I'm really torn whether I should tell her. Everyone in the family knows what he's like but she appears none the wiser. We'd all hoped he'd be found out organically before things got too serious between them but this has been going on for years now and they're on the brink of a big commitment to each other.
Any experiences or advice would be welcome.

I think you should tell his Girlfriend She Deserves so much better than him

OP - Please TELL HER!! And do it ASAP!
Please don’t ruin her life.

It doesn’t matter if your brother finds out it was you. I would want him to know it was me, if I were in your shoes. Been there, done that!
He will get over it. It’s for his own good too, anyway. He needs to realise there’s a consequence for his actions. Hopefully, it will make him do better in future (wishful thinking!).

Anonymous email. Set up one for this purpose, either a disposable one or one of the free high security ones where it can't be traced to anyone - Google for information on this. Email her, tell her the score and give enough evidence so that she can't just dismiss it.

She needs to know, but be under no illusions that it'll cause trouble if he finds out you told her. Sadly the messenger tends to be in the firing line. So protect yourself, do it anonymously and never admit to it. You can always say 'you look really worried, is everything ok?' when you see her and try to open up a conversation where you can be supportive.

Are you prepared to never speak to your brother again and for the whole family to blame you when shit hits the fan? Because that is what will happen. For the sake of a woman who probably knows it's all true but is too insecure to admit it to herself and you won't change that.

I feel sorry for the woman but I think you need to look out for yourself. Your brother has already twisted the whole family to lie for him, it's not that far fetched that he will turn them against you too.

I personally wouldn't want a relationship with a brother who did that anyway.......and wouldn't be bothered with family who condoned it.....I mean this whole thing is only going to get worse......more than likely with kids involved and they'll all be suffering from it!

Its not like if you say nothing then your brother and this girl will live happily ever after so telling will have been pointless.

It doesn't necessarily sound like the brother has had to do much twisting to get the whole family to lie for him, more like they just won't step up and do the right thing.

@baddabingbongbang
What did you decide to do ?