What is the ruling on the brother's disposal of the funds of his deceased maternal uncle and his sick mother, and is he entitled to invest all of it without dividing the inheritance?

The Sharia prohibits assaulting people's property through deception and falsehood, as Allah the Almighty says: "And do not consume one another's properties unjustly or give it to the rulers in order that you may consume a portion of the properties of others sinfully while you know" [Al-Baqarah: 188]. And the Hadith states: "Indeed, you bring your disputes to me, and perhaps some of you are more eloquent in presenting their arguments than others. So, if I rule in favor of someone by giving them a portion of their brother's right based on their words, then I am only cutting off for them a piece of fire."

A brother taking his ill mother's money or his maternal uncle's money through illicit means such as an unauthorized power of attorney or guardianship, or through bribes, is an act forbidden by Sharia. This indicates greed and disregard for the Afterlife.

The questioner must admonish her brother. If he does not respond, she must raise the matter with the Sharia courts to investigate her maternal uncle's rightful heirs and prevent her brother from trespassing on the funds. It is certain that a paternal cousin's daughter does not inherit.