Is the deceased father's will to allocate one-third of his wealth for the marriage of his minor children after his death valid, and does it clear his conscience, and are the elder siblings obligated to marry off their younger orphaned siblings?

The orphan, according to Islamic law, is one whose father died before their puberty. The status of orphanhood ceases upon reaching puberty, which is considered to be at the age of fifteen. The father's will concerning his two daughters is neither valid nor binding on the heirs, because "there is no will for an heir," unless the rest of the heirs approve it, provided they are adult and of sound judgment. The two brothers are not legally obligated to marry off their two sisters, but it is commendable for them to do so due to the reward involved and the upholding of kinship ties.