Is money resulting from the sale of a medication not used by the deceased considered part of the inheritance? And is it permissible for the questioner to benefit from it after her mother and siblings relinquished their shares to her, knowing that her brother is a minor?

Everything owned by the deceased enters into their estate after their death, and the heirs share in it. A gift from brothers of part of their share is valid if made by an adult. However, the gift of a minor is not valid. The disposition of those legally incapacitated for their own benefit, such as a child, an insane person, or a profligate (spendthrift), is not valid without prior permission. Accordingly, the sister's gift is valid because she has reached puberty, and the brother's gift is valid if he has reached puberty (by seminal emission or by reaching the age of fifteen) or if the signs of puberty have appeared on him.