Am I entitled to a share in a building constructed on land registered partly in my name and partly in my brothers' names, knowing that my brothers paid all the construction costs?

If the land is owned by the questioner, and the construction by the brothers upon it was a gift, then the building belongs to the questioner. However, if it was not a gift, then the matter is to be considered:

If they built with the permission of the questioner, they are partners in the building.

If they built without the permission of the questioner, but with the intention that the building would belong to him and that they would claim its value from him, then the building belongs to him and its value is a debt owed to these brothers.

If they built without the permission of the questioner and with the intention that the building would belong to them, then this is usurpation.