What is the ruling on taking money from one's family without their knowledge to buy essentials for the house, including things they prohibit buying?

It is not permissible to take someone else's money without their consent. Not every family member is authorized to do so. The person responsible for the essentials might have other priorities. Therefore, taking his money without his knowledge to buy what you desire is considered an تجاوز (transgression) and an unauthorized disposal of his money. This is not permissible, as it involves violating the sanctity of people's wealth, based on the saying of the Prophet (peace be upon him): "Indeed, your blood and your wealth are sacred to you, like the sanctity of this day of yours, in this month of yours, in this city of yours."