What is the ruling on one who betrayed a trust by stealing the papers that prove his relinquishment of his share, causing family problems, claiming that he is entitled to half based on custom and not on Islamic law? Is custom considered a valid proof in this case? Is my brother entitled to take half of my money that I sent him or a part of it, and what is the basis for that in Islamic law? Is he entitled to claim half of the plot of land in Cairo?

A piece of advice: do not forget the favor between you and your brother, and appreciate his medical circumstances and needs. Allah has urged the fulfillment of trusts, saying: "Indeed, Allah commands you to render trusts to whom they are due." And the Prophet, peace and blessings be upon him, said: "Render the trust to the one who entrusted you, and do not betray the one who betrays you." The Prophet made the betrayal of a trust a sign of hypocrisy: "The signs of a hypocrite are three: when he speaks, he lies; when he promises, he breaks his promise; and when he is entrusted, he betrays." Your brother does not have the right to take half of your money except with your consent. However, if he served you in your absence and managed your money, he deserves a customary wage if his action was not voluntary, and experts can estimate this amount.