Twin brothers

Before I continue with the analysis of my games, I will publish one study, which left very deep impression on me, and one guy from Republic of Ireland.
White is on move, and his task is to win this position, that at the first look seems insane, as always in the studies.
For those who want to solve it by themselves, it is better not to look at the rest of the text, as it contain spoilers.
Please keep in mind the title of this article, and I will tell you that I did not referred it to the passed pawns on a2 and b2....





As I said into introduction, I shall show the right solution.
The very first move is:

1. Bb1!

It is obvious what would happen if Black does not promote with a check.
A move 1. g7 fails to deliver the right result due to 1...a1Q+ 2. Kb5, b1Q+!.
You can calculate the rest on your own.

1...a1Q+
2. Kb5!

It looks as everything is over.
The obvious try 2...Qa3 does not work after 3. g7.

2...Bg3!
3. g7, Bb8!

This is the point of Black´s defence.
White can not promote his pawn to a queen, as Black would be stalemated, after some desperado checks by his queen!
There is no point to think about underpromotion as Black has a queen and would be ahead in a material.
Also if White advance with his f pawn, for example:

4. f6, Qa3  and it is a draw.

One of this sentences are not correct.

4. g8B!!

Now there is no stalemate, and the threat is Bd5#.

4...Bf4  ....or anywhere on the diagonal.

5. Bga2

These bishops on b1 and a2 are my twin brothers from the title.
I will not explain this study further, as everyone can win it without difficulties.