Is it obligatory to deduct the value of debts from the deceased's estate before distributing it among the heirs, and is it permissible for the eldest brother to conceal the true value of the inheritance from the other heirs if some of them are aware and their rights are guaranteed?

If a mother needs medical treatment and does not possess the funds, her capable children are obligated to provide for her treatment, as treatment is part of the maintenance (nafaqah (definition)) that is incumbent upon them. If the children incur debt for her treatment, they have the right to reclaim the money from the mother when she becomes able, or from her estate after her death, provided they had this intention at the time of incurring the debt. Otherwise, they will be considered as having made a donation. As for settling the debt from the inherited property from the father, if the question is about recovering the debt from the mother's share, then it is detailed as mentioned. If the intention is to settle the debt from the children's share before division, then this depends on the intention of the sibling who incurred the debt and the agreement of the heirs. Adult and mature heirs must disclose the true extent of the inheritance to everyone. If there is a minor among the heirs, their share will be under the care of their guardian.