All names in this are fake for privacy reasons. And this might be long with alot of context, so brace yourself.

Me and my oldest brother Danny are, and always have been, close. He has always been my guardian angel. When I needed support, he supported. When I needed kindness, he was kind. When I needed a friend, he was a friend. He has a heart of gold and a will of iron. And he is probably the closest person in my life other than my partner (34f). He has always been there for me, and I can't think of a single place where he fails as a human being. He is a model big brother.

So, when he got out of the army (was in from 18 to 24) he met a girl - let's call her Sue (currently 38f). They seemed to click. I really liked Sue, like the rest of our family. I honestly was so happy my brother met someone whom he loved and who made him happy. She was a nice sister in law too. So of course, I was delighted when they had a daughter together (though becoming an aunt at 20 was definitely an odd feeling, for some reason), followed by two sons (currently 10m and 8m).

I don't know if it's just his talents for being nurturing and caring and strong, or if he had a cheat sheet written by God, but my brother just took to being a dad. Seriously, his kids are all these amazing, smart quirky little characters just bursting with life and potential. Even people who aren't big on kids love being around them. This, is in no small part to my brother. He busted his ass to raise them right and showed them levels of affection and care that all kids should have.

But his daughter, let's call her Rachel. Now, my brother loves his sons with all his heart. He doesn't have favourites. But Rachel... well, her place in his heart was special. I don't know if it was because she was the firstborn, or if she was the only girl but they just have this bond. My brother has imparted so much of himself onto her, she's basically the female him. A total daddy's girl (in a good way) and my brother's absolute treasure.

Well, recently Sue's reoccurring struggle with depression popped up. Danny, by her account, is amazing at these points and really pulls her through. Well, apparently last week she needed to pour her heart out and what poured out was a bullet in the heart for my brother.

Rachel isn't biologically his.

Around the time she got pregnant, she had cheated. And that guy was the father, but she hadn't told Danny (which had probably been a big contributor to her depression). Before this, everyone had assumed Rachel had simply received an odd mesh of Danny and Sue's facial features, very strongly resembling neither - the hair, eye colour, and very basic facial structure matched Danny. I suppose Sue had a type. The boys are his (they couldn't be anyone elses, seriously they are his clones) but Rachel... wasn't.

My brother left right away. He and Sue are over. I think she knew that would happen. My brother would never tolerate it, not for a moment. And finding out 12 years, three kids and a chunk of your life later adds a level of pain I'm not even going to pretend I can comprehend. I cried when I found out. God sake, my partner cried when we found out. That night was a fucking nightmare.

My brother is currently living with a friend. We've spoken, and it should tell you how close we are that I am the only person aside from them friend he is living with, that he has spoken to. When I speak to him about his kids, he just says "the boys" as if Rachel isn't a part of things. When I mention her, he goes nuts and breaks down. She isn't his, he's saying. But I can tell that has really fucking broken him.

To make matters worse, the kids are desperate to see their dad. They get it - they're parents are separating. But they are desperate to see my brother again. But I don't think he can bare to face them. He's as low as he's ever been in his life right now and I have no idea what to do. Rachel is most hysterical of all. And it breaks my heart that she called me and asked if it was something she did. All I could say was no, and that her dad loves her very much and he's just visiting a friend and we all love her very much and I couldn't stop crying.

I want to grab my brother and tell him - look at this girl. This little girl who carries books around and reads books I probably couldn't because you read to her every night since she was born. This girl who mimicks your behaviours. This girl who worships you and depends on you. This little girl who is breaking down in tears to see her dad. Does eleven years of love not hold any weight against biology?

But I can't do it. I just can't bring myself to tell my brother to do that. I can't understand what he's going through and I can't tell him what to do.

But I need to help him, if I even can. And I need to help Rachel, if I even can. This whole situation is heart-rending for everyone. But I feel I am maybe the only person in a position to help here.

Tldr - Brother's much loved daughter is not his. He's been at a friends for a week, only contacting me. Want to help. Need advice.