"my friend, my brother"

How do you say "my friend, my brother" in Polish?

mój brat I think is Polish for my brother but my Polish isnt reliable.

Mój przyjaciel/przyjaciółka
male/female

Mój brat is right

male friend?

znajomy ( person one knows)
kolega (at work, school)
przyjaciel ( person one likes)

Very close male friend whom I have known for thirty years who is like a brother.

For the friend part: przyjaciel or kumpel. Przyjaciel stresses affection (bordering on and including non-romantic love) and kumpel stresses shared experience from long acquaintance (I'm not a native speaker of Polish but it seems that's how the words are used).

You could also just call him brat (brother, 'my' isn't necessary in Polish) but sibling relationships are as compicated in Poland as anywhere else so maybe you're safer with friend.

Also if you're adressing him directly kumpel doesn't work, I think, and the forms would be

przyjacielu,

bracie

I second that.

Edit.
Actually you could use 'my' here, imho it would stress the affection

Mój przyjacielu, mój bracie!

or
Przyjacielu mój, bracie!

Why do you add a U on the end of przyjacielu? I had the same word but without one from my dictionary.

przyjaciel - nominative case
przyjacielu - vocative case

That's my friend - to jest mój przyjaciel (you're speaking about a person)
Tell me, my friend. - Powiedz, mój przyjacielu (you're speaking directly to that person)

Thank you, all.