Positive or negative?

No that would not do any good to tell him.

But it would probably make you feel better.

No, sadly some people are only happy when they are pessimistic.

It's being so cheerful wot keeps them going! ( as we used to say about any old miseries.)

Maybe he 'enjoys poor health' as some people seem to. It feels like they can only define themselves in this way. Sad really.
What a lovely cheerful friend you have though. A terrific inspiration.

Watermeadow your post reminded me so much of my late FIL. Always gloomy, health problems worse than anyone else etc etc. I came to the conclusion he enjoyed being the way he was, he never changed and I don't think your brother will.As rosesarered has said " it's being so cheerful that keeps them going" He is obviously a "glass half empty person". I can only suggest you keep yours overflowing.

Buy your brother a bottle of 'happy pills' for xmas I live in a small community and theres a woman who is just like your brother, I avoid her at all costs!

As Jane wrote, mayb he has a health problem, or doesn't sleep well; Like me - if I have a bad night I'm all doom and gloom the next day. But after a good night, I'm all optimistic.
Very trying for you though, watermeadow.

Sounds like DH. Takes after his late mother. Her grandchildren called her Nana No No. She thought that was great.

Could you say something gently to your brother Watermeadow? It is easy to get into a rut of expressing negative viewpoints almost without noticing. I'm sure a lot of us would benefit from trying to have a more positive outlook!