Whatsoever a father gives to his children during his life time it is not ‘inheritance’ rather it is a gift and hibah from father. And while giving gift it is required that father maintains equality among all his children. If he has any daughters he should give them also. It is also necessary for the completion of hibah that the share of legatee is given into his complete possession except the things which are indivisible. Hence in the above mentioned case if your father did not give the share of each son into their complete possession then the hibah was not valid rather it remained in the possession of your father as usual. If he wants to give in gift then he should divide it afresh and give equal shares to all the sons as well as to his daughters if he had. And he should also give the share of each son and daughter into their complete possession. In case he gave the share of each son into their complete possession then it was valid as per the Shariah. Now it is not lawful to take it back from them. In such a case the father has more cash or property etc then he should give something from it to you so that your share is equal.
Allah knows Best!
Darul Uloom Deoband