What is the ruling on demanding reimbursement for expenses paid to my mother, father, and siblings from my mother's estate after her death, and do I have the right to reclaim what I previously paid to them?

It is permissible to demand the debt you paid to your mother after her death, and to take it from her estate before its distribution among the heirs. This is because debt takes precedence over the heirs' right to the money. However, during the mother's lifetime, there is a difference of opinion regarding the permissibility of a child demanding a debt from her. The four madhhabs (schools of thought) permitted this, while the Hanbalis specifically restricted the prohibition to the father, not the mother. Sheikh Ibn 'Uthaymeen, however, favored the view that a child should not demand a debt from his mother, just as he should not from his father. But after her death, the son may take the debt from his mother's estate, because the debt has not been waived from her; rather, the demand for it was merely delayed.