What is the ruling on disposing of the money of heirs, including a minor, before it has been divided, by spending it on renovating a rented house, purchasing furniture, and on personal matters?

The guardian of an orphan's wealth must preserve it and spend from it for the orphan's needs in a reasonable manner if no one else donates. It is permissible for the guardian to mix the orphan's money with his own, and to consume from it reasonably if he is poor. An orphan is one whose father died before he reached puberty. Therefore, if your brother had not reached puberty, you erred in disposing of his money by renovating and furnishing the house and taking some of it for yourself. The obligation was to limit spending to his essential needs and preserve the rest for him. What was disposed of unlawfully must be returned to him, because it is forbidden for a guardian to act except in what benefits the ward.