All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His Slave and Messenger.
As regards inheritance, it is an entitlement after death. If a person dies, his inheritance is divided amongst his children according to the division prescribed by Allaah; and it is not permissible to gift one child without gifting the other children; rather, it is an obligation to be just with them when gifting them. If he favors one of his children over others, he is obliged to repent to Allaah, and take back what he had gifted the first child [so that it will be added to the inheritance] or gift his other children in the same manner he had gifted that child. He should fear the punishment and displeasure of Allaah, as not being just between the children is an injustice that is prohibited by Allaah and by His Prophet .
As regards whether or not Hajj wipes away this sin, then this is something that only Allaah knows. However, all people will receive their due rights by the Day of Judgment.
For more benefit, please refer to Fatwa 81549 and 92219.
Allaah Knows best.