Is it considered deception against the state and unlawful for a brother to refuse to register his house in his name with government agencies—for the sake of an additional pension he receives, which harms the rest of the heirs in establishing the mother's will?

If the additional pension is a conditional grant from the state for a specific category, then it is not permissible for someone who does not meet the conditions to take it through trickery and deception, otherwise they would be consuming wealth unjustly, based on the Almighty's saying: "O you who have believed, do not consume one another's properties unjustly," and the Prophet's (peace be upon him) saying: "Whoever cheats is not one of us," and "Muslims are bound by their conditions."