What is the ruling on the third brother taking money as compensation for the shares of his two brothers, given that he did not participate in the building at that time due to his young age?

It is permissible for the two sons who lent money to their father to take their debt from the inheritance before it is divided among the heirs, and the third son has no right to object. This is due to the consensus of the majority of jurists on the permissibility of a son demanding from his father a debt owed to him. Even the Hanbalis, who prohibited such a demand during the father's lifetime, permitted taking from the inheritance after his death, as presented by Ibn Qudamah in Al-Mughni and Al-Mardawi in Al-Insaf. Thus, the two sons have the right to collect their debt and then take their share of the inheritance. What the youngest son took unlawfully is not permissible for him, and his claim that he would have lent money to his father had he been older has no legal weight.