Is it permissible for the legally responsible individual who managed the estate of his deceased father, and divided the inheritance between his mother and his father's wife, without taking his own share due to his ignorance, to retroactively deduct his rightful share and then give the remainder to the heirs?

You have a share in the inheritance because the entitlement to inheritance is related to the degree of kinship to the deceased, not age. Allah Almighty says: (For men is a share of what the parents and close relatives leave, and for women is a share of what the parents and close relatives leave, be it little or much - an obligatory share). Justice in distributing the inheritance is according to the Sharia shares, not equally, so the share of a male differs from the share of a female. Allah Almighty says: (Allah instructs you concerning your children: for the male, what is equal to the share of two females...). You must submit a case for the division of the inheritance to the competent authorities in your country, especially since these are properties that have not yet been divided. This is safer for your religion and prevents any future disputes.